# NIOS Class 10 Science and Technology Chapter 13 Work and Energy

NIOS Class 10 Science and Technology Chapter 13 Work and Energy Solutions to each chapter is provided in the list so that you can easily browse through different chapters NIOS Class 10 Science and Technology Chapter 13 Work and Energy and select need one. NIOS Class 10 Science and Technology Chapter 13 Work and Energy Question Answers Download PDF. NIOS Study Material of Class 10 Science and Technology Notes Paper 212.

## NIOS Class 10 Science and Technology Chapter 13 Work and Energy

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 10 Science and Technology Chapter 13 Work and Energy, NIOS Secondary Course Science and Technology Solutions for All Chapters, You can practice these here.

### Work and Energy

Chapter: 13

INTEXT QUESTIONS 13.1

1. Choose the correct option.

(i) Work done is zero:

(a) When force and displacement are in the same direction.

(b) When force and displacement of the body are in opposite directions.

(c) When force acting on the body is perpendicular to the direction of the displacement of the body.

(d) When force makes an angle with displacement.

Ans: (c) When force acting on the body is perpendicular to the direction of the displacement of the body.

(ii) 1 J of work is done when a force of 0.01 N moves a body through a distance of:

(a) 0.01 m.

(b) 0.1 m.

(c) 1 m.

(d) 10 m.

(e) 100 m.

Ans: (e) 100 m.

(iii) In which of the following situations work is done?

(a) A person is climbing up a staircase.

(b) A satellite revolving around the earth in closed circular orbit.

(c) Two teams play a tug of war and both pull with equal force.

(d) A person is standing with a heavy load on his head.

Ans: (a) A person is climbing up a staircase.

2. A car of mass 500 kg is moving with a constant speed of 10 ms–1 on a rough horizontal road. Force expended by the engine of the car is 1000 N. Calculate work done in 10 s by:

(a) Net force on the car.

(b) Gravitational force.

(c) The engine.

(d) Frictional force.

Ans: (c) The engine.

INTEXT QUESTIONS 13.2

1. Explain the terms work and energy with one example each.

Ans: Work is said to be done when force is applied on a body and the body moves through some distance in the direction of force.

Example: A person climbing up a staircase.

Energy: The ability to do work is called energy.

Example: A weightlifter lifts the weight.

2. The ability to do work is called ……………

Ans: Energy.

3. The SI unit of all forms of energy is ……………

Ans: Joule.

4. Energy possessed by a spring is …………… energy.

Ans: Potential.

5. The energy possessed by a body due to its position is called …………… energy.

Ans: Potentia.

6. The energy possessed by a body due to its motion is called …………… energy.

Ans: kinetic.

7. At height h the potential energy is Ep at height 2 h the potential energy would be ……………

Ans: Ep/2.

8. At height h the potential energy of a body of mass m is Ep. At the same height the potential energy of a body of mass 2 m would be ……………

Ans: Ep/2..

9. A body of mass m moving with a speed v has kinetic energy, Ek. The body if moves with speed 2v, will have kinetic energy equal to ……………

Ans: 4Ek..

10. A body of mass m moving with a speed v has kinetic energy Ek. A body of mass 2m moving with the same speed will have a kinetic energy…………..

Ans: 2Ek..

INTEXT QUESTIONS 13.3

1. Give one example each of the following energy transformations.

(i) Light energy into chemical energy.

Ans: In photosynthesis green plants transform light energy into chemical energy of carbohydrates.

(ii) Chemical energy into heat.

Ans: In digestion of food chemical energy of food is converted into heat.

(iii) Chemical energy into electrical energy.

Ans: Electrical cells convert chemical energy into electrical energy.

(iv) Mechanical energy into electrical energy.

Ans: In electric generators mechanical energy is converted into electrical energy.

(v) Thermal energy into electrical energy.

Ans: In thermal power plants heat energy is converted into electrical energy. (Note: a still better example would be a thermocouple which directly converts heat energy into electrical energy).

(vi) Light energy into electrical energy.

Ans: In Solar Cells Light energy is converted into electrical energy.

2. (i) A motor converts electrical energy into …………………

Ans: Mechanical energy.

(ii) An electric heater converts  electrical energy into …………………

Ans: Heat energy.

(iii) A microphone converts sound energy into …………………

Ans: Electrical energy.

(iv) A loudspeaker converts sound energy into …………………

Ans: Electrical energy.

(v) A heat engine converts heat energy into …………………

Ans: Mechanical energy.

(vi) When we rub our hands together we change work into …………………

Ans: Heat energy.

INTEXT QUESTIONS 13.4

1. Kamya climbs up a staircase in 5 minutes, Suraiya takes only 3 minutes in going up the same staircase. The weight of Kamya is equal to the weight of Suraiya.

(i) Which of the two does more work?

Ans: They both do work against gravity. Because both of them have equal weight and climb equal height they do equal work.

(ii) Which of the two spends more power?

Ans: Because Suraiya takes lesser time in climbing up the staircase and power is inversely proportional to time so, Suraiya spends more power.

2. Express 1.5 H.P. in SI Unit of power.

Ans: SI unit of power is watt and

1 H.P. = 746 watt

1.5 H.P. = 746 × 1.5 = 1119.0 watt = 1.12 kW.

3. One cricket ball and One plastic ball are dropped from the same height. Which will reach the ground with:

(a) More energy

Ans: Cricket ball.

(b) Less power?

Ans: Plastic ball.

1. Define the following terms and give their SI units.

(a) WorK.

Ans: Works: The term work is used when there is a displacement of an object by applying some amount of force to it. Its SI unit is N-S.

(b) Power.

Ans: Power is denoted by the amount of work done in a certain time. The unit of power is watt.

(c) Energy.

Ans: The energy is considered as the efficiency of doing some work.

2. List different forms of energy.

Ans: Energy exists in many different forms. Examples of these are: light energy, heat energy, mechanical energy, gravitational energy, electrical energy, sound energy, chemical energy, nuclear or atomic energy and so on. Each form can be converted or changed into the other forms.

3. State Law of Conservation of Energy. Explain with the help of examples.

Ans: The law of conservation of energy states that energy cannot be created or destroyed. However, it can be converted from one form to another form or transferred.

For example: an object falling from a certain height converts its potential energy to kinetic energy and at all instant total mechanical energy remains constant.

4. List the energy transformation taking place in a thermal power plant.

Ans: Thermal power plant → Chemical energy → Heat energy → Electrical energy.

5. A ball of mass 0.5 kg has100 J of kinetic energy. What is the velocity of the ball?

Ans: As we know, kinetic energy (Ek) = 1/2mv^2;

Or, 100 = 1/2×0.5×v^2;

Or, v = 20m/s.

6. A body of mass 100 kg is lifted up by 10 m. Find (a) The amount of work done.

(a) The amount of work done.

Ans: 100000 J.

(b) Potential energy of the body at that height (g = 10ms2

Ans: The work done, w = F×S,

Here, f = m×a = 100×10 =1000; s =10m.

So, w = 1000×10 = 10^4 NS.

Potential energy = mgh,

Here, m = 100 kg, g = 10m/s^2, h = 10m.

Potential energy = 100×10×10 = 10^4.

7. Why road accidents at high speeds much worse than the accidents at low speeds?

Ans: The most of the road accidents nowadays happen because of the high speed. As we know the kinetic energy is maximum when the speed is high and low when speed is low so more fatal damage happens in case of high kinetic energy.

8. Two bodies of equal mass move with uniform velocities u and 4 u respectively. Find the ratio of their kinetic energies.

Ans: The kinetic energy = 1/2mv^2;

So, kinetic energy id directly proportional to the velocity.

Ek (1)/Ek (2) = ¼.

9. What would you like to prefer a ramp or a staircase to reach at the third floor of your hospital? Justify.

Ans: We always try to do small amounts of work for the purpose of working days. In this case, as in the ramp there is no way of doing heavy work and in this case we have to do more work so the ramp is preferable.

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