NIOS Class 10 Science and Technology Chapter 13: WORK AND ENERGY– Chapter-wise Important Questions and Answers

NIOS Class 10 Science and Technology Chapter 13: WORK AND ENERGY | MCQs, Short & Long Answer Questions | 13: WORK AND ENERGY

Chapter 13: WORK AND ENERGY

INTEXT QUESTIONS 13.1

Choose the correct option

1. (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

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

[ Work is done only when force causes displacement in its own direction. If force acts perpendicular to displacement, it does not move the body in that direction, so work done is zero.]

 

(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

Answer: (e) 100 m

[ We know that,  work done = force × distance
       1 J = 0.01 N × Distance
Distance

=10.01 = 100 m

Therefore, 1 J of work is done when a force of 0.01 N moves a body through 100 m distance.

 

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

(a) A person is climbing up a stair case.

(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 heavy load on his head.

(a) A person is climbing up a staircase.

[ Work is done when force causes displacement. While climbing stairs, the person applies force and moves upward, so work is done. In the other cases, there is no displacement in the direction of force.]

 

2. A car of mass 500 kg is moving with a constant speed of 10 m/s 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

Answer: Given, Mass of car = 500 kg , Speed = 10 m/s  , Engine force = 1000 N and Time = 10 s
Distance = Speed × Time = 10 × 10 = 100 m

(a)  Since the car moves with constant speed, acceleration = 0, so net force = 0.
Work done = 0 J

(b) Gravitational force acts vertically downward, but displacement is horizontal.
Work done = 0 J

(c)  Work = Force × Distance
= 1000 × 100
= 100000 J

Work done = 100000 J=105 J

(d) Since speed is constant, frictional force = engine force = 1000 N and acts opposite to motion.
Work = – Force × Distance
= –1000 × 100
= –100000 J=-105 J

Work done =-105 J

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Posted 1 week ago