Work Energy Power Competitive Exams
100 questions · General Science
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Question 1 of 100
A see-saw is an example of which simple machine?
ExplanationA see-saw pivots around a fixed point (fulcrum), which is the basic principle of a lever.
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Question 2 of 100
If the velocity of an object is doubled, its kinetic energy becomes:
ExplanationSince KE ∝ v², doubling the velocity increases kinetic energy by a factor of four.
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Question 3 of 100
The efficiency of a machine is defined as:
ExplanationEfficiency is the ratio of useful energy output to total energy input, expressed as a percentage.
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Question 4 of 100
If the mass of an object is doubled while velocity stays the same, its kinetic energy becomes:
ExplanationSince KE ∝ m, doubling the mass simply doubles the kinetic energy.
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Question 5 of 100
Hydroelectric power is generated using the energy of:
ExplanationHydroelectric plants harness the kinetic energy of moving water to generate electricity.
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Question 6 of 100
A roller coaster car at the top of a hill has mostly:
ExplanationAt the top of the hill, the car is momentarily slow-moving and high up, so its energy is mostly potential.
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Question 7 of 100
If the force applied and the displacement are perpendicular (θ = 90°), the work done is:
ExplanationSince cos(90°) = 0, no work is done when the force is perpendicular to the displacement.
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Question 8 of 100
If you push against a wall but it does not move, in the scientific sense:
ExplanationSince the wall does not move, there is no displacement, so no work is done in the physics sense, despite the effort.
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Question 9 of 100
If a force of 10 N moves an object 5 m in the direction of the force, the work done is:
ExplanationWork = Force × distance = 10 × 5 = 50 J.
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Question 10 of 100
One major advantage of renewable energy sources over fossil fuels is that they:
ExplanationRenewable sources replenish naturally and typically produce fewer harmful emissions than fossil fuels.
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Question 11 of 100
In a swinging pendulum (ignoring friction), energy continuously transforms between:
ExplanationAs a pendulum swings, energy converts back and forth between kinetic energy (at the bottom) and potential energy (at the ends).
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Question 12 of 100
Kinetic energy depends on:
ExplanationKinetic energy depends on an object's mass and the square of its velocity: KE = ½mv².
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Question 13 of 100
The SI unit of power is:
ExplanationPower is measured in watts (W), where 1 W = 1 J/s.
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Question 14 of 100
Energy is defined as:
ExplanationEnergy is the capacity or ability of a body to do work.
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Question 15 of 100
One watt is defined as:
ExplanationBy definition, 1 watt equals 1 joule of work (or energy) transferred per second.
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Question 16 of 100
A 0.5 kg object is projected upward with an initial kinetic energy of 40 J (g = 10 m/s²). Using energy conservation, the maximum height it reaches is:
ExplanationAt maximum height all KE converts to PE: 40 = mgh = 0.5 × 10 × h, so h = 40/5 = 8 m.
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Question 17 of 100
In science, 'work' is said to be done only when:
ExplanationScientific work requires a force to cause displacement of an object; simply applying force isn't enough.
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Question 18 of 100
Energy that comes from the movement of an object is called:
ExplanationKinetic energy is the energy an object has because it is moving.
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Question 19 of 100
The formula for power is:
ExplanationPower equals work done divided by the time taken: P = W/t.
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Question 20 of 100
A machine lifts a 50 kg load to a height of 4 m using 2500 J of input energy (g = 10 m/s²). The efficiency of the machine is:
ExplanationUseful output = mgh = 50 × 10 × 4 = 2000 J; Efficiency = (2000/2500) × 100 = 80%.
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Question 21 of 100
Scissors work using the principle of which simple machine?
ExplanationScissors are made of two levers joined at a pivot (fulcrum) to cut material.
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Question 22 of 100
Elastic potential energy is stored in objects such as:
ExplanationStretched or compressed elastic objects like springs store elastic potential energy.
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Question 23 of 100
A machine used to lift heavy loads using a rope over a wheel is called a:
ExplanationA pulley uses a wheel and rope to change the direction (and sometimes amount) of force needed to lift a load.
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Question 24 of 100
At the bottom of its swing, a pendulum bob has:
ExplanationAt the lowest point of the swing, the bob moves fastest (max KE) and is at its lowest height (min PE).
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Question 25 of 100
The law of conservation of energy states that energy:
ExplanationEnergy is never created or destroyed; it simply changes form while the total amount stays constant.
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Question 26 of 100
No real machine can be 100% efficient because:
ExplanationIn practice, some input energy is always lost to friction and heat, so output energy is always less than input.
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Question 27 of 100
A machine with 70% efficiency requires 1000 J of input energy. The energy wasted (e.g. as heat) is:
ExplanationWasted energy = Input − Output = 1000 − (0.70×1000) = 1000 − 700 = 300 J.
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Question 28 of 100
Lifting a box straight up against gravity is an example of doing work against:
ExplanationLifting an object vertically requires work to overcome the downward pull of gravity.
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Question 29 of 100
The general formula for work done is:
ExplanationThe general work formula accounts for the angle θ between the force and displacement: W = Fd·cosθ.
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Question 30 of 100
If a motor has a power of 100 W, the work it does in 5 seconds is:
ExplanationWork = Power × time = 100 × 5 = 500 J.
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Question 31 of 100
Wind energy is used to generate electricity using:
ExplanationWind turbines convert the kinetic energy of moving air into electrical energy.
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Question 32 of 100
A machine has an energy input of 500 J and a useful energy output of 400 J. Its efficiency is:
ExplanationEfficiency = (400/500) × 100 = 80%.
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Question 33 of 100
Sound energy is produced by:
ExplanationSound is produced when an object vibrates, creating waves that travel through air or other media.
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Question 34 of 100
If a man lifts a weight of 200 N through a height of 2 m in 4 seconds, his power output is:
ExplanationWork = 200 × 2 = 400 J; Power = Work/time = 400/4 = 100 W.
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Question 35 of 100
A 2 kg ball is dropped from a height of 5 m (g = 10 m/s²). Using energy conservation, its speed just before hitting the ground is:
ExplanationPE = mgh = 2×10×5 = 100 J = KE = ½mv², so v² = 100, giving v = 10 m/s.
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Question 36 of 100
A crate is pulled 10 m across the floor by a force of 50 N applied horizontally. The work done is:
ExplanationW = F × d = 50 × 10 = 500 J.
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Question 37 of 100
During photosynthesis, plants convert light energy into:
ExplanationPlants use sunlight to produce glucose, storing the Sun's light energy as chemical energy in food.
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Question 38 of 100
In an ideal system with no friction or air resistance, the total mechanical energy (KE + PE) of a falling object:
ExplanationWithout energy losses, total mechanical energy is conserved as the object falls, only changing form.
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Question 39 of 100
A larger power rating for the same amount of work means:
ExplanationA higher power rating means the same amount of work is completed in less time.
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Question 40 of 100
At the highest point of its path, a ball thrown upward has:
ExplanationAt the highest point the ball momentarily stops (zero KE), while its height (and so PE) is at its maximum.
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Question 41 of 100
A machine does 500 J of work in 10 seconds. Its power output is:
ExplanationPower = Work/time = 500/10 = 50 W.
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Question 42 of 100
The formula for gravitational potential energy is:
ExplanationGravitational potential energy is given by PE = mgh.
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Question 43 of 100
Gravitational potential energy depends on:
ExplanationGravitational PE = mgh, depending on mass, height, and the acceleration due to gravity.
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Question 44 of 100
Which of these is an example of electrical energy being used?
ExplanationA fan plugged into a socket uses electrical energy to run its motor.
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Question 45 of 100
An example of negative work being done is:
ExplanationFriction acts opposite to the direction of motion, so it does negative work on a moving object.
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Question 46 of 100
Fossil fuels such as coal, oil, and natural gas are classified as non-renewable because they:
ExplanationFossil fuels form over geological timescales and are consumed far faster than nature can replace them.
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Question 47 of 100
A doorknob is an example of which simple machine?
ExplanationA doorknob works as a wheel and axle, where turning the larger wheel rotates the smaller axle.
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Question 48 of 100
Geothermal energy is derived from:
ExplanationGeothermal energy comes from the natural heat stored deep within the Earth.
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Question 49 of 100
Which simple machine is used in a ramp to help move a heavy box up to a truck?
ExplanationA ramp is a classic example of an inclined plane, reducing the force needed to raise an object.
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Question 50 of 100
Simple machines make work easier mainly by:
ExplanationSimple machines do not create energy; they change the direction or magnitude of the force required to do a task.
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Question 51 of 100
Which of the following best helps increase the mechanical efficiency of a machine?
ExplanationReducing friction (e.g., with lubrication) reduces wasted energy, improving overall efficiency.
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Question 52 of 100
A 2 kg object moving at 3 m/s has a kinetic energy of:
ExplanationKE = ½mv² = 0.5 × 2 × 3² = 0.5 × 2 × 9 = 9 J.
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Question 53 of 100
Negative work is done when:
ExplanationWhen the force opposes the direction of motion, the work done by that force is negative.
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Question 54 of 100
A battery stores which type of energy?
ExplanationA battery stores chemical energy, which is converted into electrical energy when used.
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Question 55 of 100
Which of the following is an example of energy transformation from electrical to sound energy?
ExplanationA loudspeaker converts electrical signals into sound waves.
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Question 56 of 100
A 1000 kg car moving at 20 m/s is brought to rest using its brakes. The work done by the brakes equals the car's initial kinetic energy, which is:
ExplanationKE = ½mv² = 0.5 × 1000 × 20² = 0.5 × 1000 × 400 = 200000 J.
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Question 57 of 100
As a ball falls freely from a height, its potential energy:
ExplanationAs height decreases during the fall, potential energy converts into kinetic energy.
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Question 58 of 100
The SI unit of work is the:
ExplanationWork is measured in joules (J) in the SI system.
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Question 59 of 100
Which form of energy do we get from burning wood?
ExplanationBurning wood releases stored chemical energy as heat and light.
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Question 60 of 100
The formula for kinetic energy is:
ExplanationKinetic energy is calculated as one-half times mass times velocity squared.
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Question 61 of 100
A force of 20 N is applied at an angle of 60° to a 4 m displacement. The work done is approximately (cos60° = 0.5):
ExplanationW = F×d×cosθ = 20 × 4 × 0.5 = 40 J.
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Question 62 of 100
A car engine delivering a constant force of 2000 N while moving at 15 m/s has a power output of:
ExplanationPower = F × v = 2000 × 15 = 30000 W.
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Question 63 of 100
A man pushes a wall with a force of 100 N but the wall does not move. The work done on the wall is:
ExplanationSince there is no displacement of the wall, the work done is zero regardless of the force applied.
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Question 64 of 100
A screw works like a simple machine that is essentially a:
ExplanationA screw's thread is essentially an inclined plane wrapped around a cylinder.
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Question 65 of 100
Plants get their energy mainly from:
ExplanationPlants use sunlight through photosynthesis to produce their own food and energy.
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Question 66 of 100
Which of the following is a non-renewable source of energy?
ExplanationCoal is a fossil fuel that takes millions of years to form and cannot be quickly replaced.
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Question 67 of 100
Which of the following is a source of light energy?
ExplanationThe Sun is the main natural source of light (and heat) energy for the Earth.
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Question 68 of 100
Which of the following correctly relates power, force, and velocity for constant force along the direction of motion?
ExplanationFor a constant force along the direction of motion, power equals force multiplied by velocity: P = Fv.
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Question 69 of 100
An axe is an example of which simple machine?
ExplanationAn axe blade is a wedge, which concentrates force into a small area to split material.
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Question 70 of 100
Biomass energy is obtained from:
ExplanationBiomass energy comes from burning or processing organic matter like wood, crop waste, and plant material.
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Question 71 of 100
A motor is 75% efficient and uses 800 J of input energy. The useful output energy is:
ExplanationOutput = Efficiency × Input = 0.75 × 800 = 600 J.
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Question 72 of 100
Which is a correct example of 'no work being done' in the scientific sense?
ExplanationSince the box does not move while being held, there is no displacement, so no work is done on it, even though effort is used.
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Question 73 of 100
The energy stored in food that gives us energy to work and play is called:
ExplanationFood stores chemical energy, which our bodies convert into energy for activity.
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Question 74 of 100
Which of the following has the same units as work?
ExplanationWork and energy are both measured in joules and are dimensionally equivalent.
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Question 75 of 100
An electric heater converts electrical energy to heat at a rate of 1000 W. The energy consumed in 2 minutes is:
ExplanationEnergy = Power × time = 1000 × (2×60) = 1000 × 120 = 120000 J.
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Question 76 of 100
Energy that is stored due to an object's position (like a ball on a hill) is called:
ExplanationPotential energy is stored energy due to an object's position or height.
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Question 77 of 100
Nuclear energy is released from the nucleus of atoms mainly through the process of:
ExplanationNuclear energy is released when atomic nuclei split apart (fission) or combine (fusion).
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Question 78 of 100
Heat energy from the Sun is also called:
ExplanationHeat received from the Sun is called solar or thermal energy.
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Question 79 of 100
Work done against gravity when lifting an object of weight W to a height h is given by:
ExplanationThe work done to lift an object equals its weight multiplied by the height raised: Work = W×h.
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Question 80 of 100
A ball held at a height above the ground possesses:
ExplanationA stationary ball held at height has potential energy due to its position, but no kinetic energy since it is not moving.
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Question 81 of 100
Work done depends on:
ExplanationWork equals force multiplied by the displacement in the direction of that force.
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Question 82 of 100
A pump raises 500 kg of water through a height of 10 m in 25 seconds (g = 10 m/s²). The power of the pump is:
ExplanationWork = mgh = 500 × 10 × 10 = 50000 J; Power = 50000/25 = 2000 W.
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Question 83 of 100
In a car engine, chemical energy stored in fuel is converted mainly into:
ExplanationBurning fuel releases chemical energy, which the engine converts into mechanical motion, with some lost as heat.
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Question 84 of 100
A 5 kg box is lifted vertically through a height of 2 m (g = 10 m/s²). The work done against gravity is:
ExplanationWork = mgh = 5 × 10 × 2 = 100 J.
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Question 85 of 100
Which of the following is considered a clean and renewable source of energy?
ExplanationSolar energy is continuously available from the Sun and produces no direct emissions during use.
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Question 86 of 100
When we switch on a light bulb, electrical energy is converted into:
ExplanationA light bulb converts electrical energy mainly into light energy, with some heat also produced.
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Question 87 of 100
In a hydroelectric power plant, falling water's potential energy is converted into:
ExplanationFalling water's potential energy becomes kinetic energy, which turns turbines to generate electrical energy.
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Question 88 of 100
A crane does 20000 J of work to lift a load in 8 seconds. The power developed by the crane is:
ExplanationPower = Work/time = 20000/8 = 2500 W.
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Question 89 of 100
Horsepower is a unit used to measure:
ExplanationHorsepower, like the watt, is a unit of power (rate of doing work).
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Question 90 of 100
A solar panel converts sunlight into:
ExplanationSolar panels use the photovoltaic effect to directly convert light energy into electrical energy.
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Question 91 of 100
A ball of mass 0.2 kg falls freely from rest through a height of 20 m (g = 10 m/s²). Its kinetic energy just before hitting the ground is:
ExplanationBy energy conservation, KE = PE = mgh = 0.2 × 10 × 20 = 40 J.
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Question 92 of 100
Two machines A and B do the same amount of work, but A takes half the time B takes. Compared to B, machine A has:
ExplanationSince Power = Work/time and A completes the same work in half the time, A's power output is twice that of B.
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Question 93 of 100
Carrying a heavy bag while walking on level ground, holding it steady, involves:
ExplanationSince the force holding the bag up is perpendicular to the horizontal motion, no work is done on the bag in the direction of travel.
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Question 94 of 100
A wound-up toy car uses which form of stored energy to move?
ExplanationWinding up the toy stores elastic potential energy in its internal spring, which is released to drive the wheels.
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Question 95 of 100
A crane lifts a 1000 N load to a height of 10 m in 20 seconds. The power developed is:
ExplanationWork = 1000 × 10 = 10000 J; Power = 10000/20 = 500 W.
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Question 96 of 100
A wheelbarrow uses the principle of a:
ExplanationA wheelbarrow acts as a lever, with the wheel as the pivot point (fulcrum).
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Question 97 of 100
A simple machine that makes work easier using a flat sloped surface is called a(n):
ExplanationAn inclined plane is a flat, sloped surface used to raise objects with less force.
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Question 98 of 100
Which of the following is a renewable source of energy?
ExplanationSunlight is a renewable source because it is continuously available and does not get used up.
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Question 99 of 100
A 4 kg object is raised to a height of 5 m (g = 10 m/s²). Its potential energy is:
ExplanationPE = mgh = 4 × 10 × 5 = 200 J.
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Question 100 of 100
Power is defined as:
ExplanationPower measures how quickly work is done, i.e., work done per unit time.
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