A person A pushes a body of 5 kg placed on a rough surface of co-efficient of friction 0.3 by a distance of 4 m in 15 seconds. Another person B pushes the body of 7 kg on same surface by a distance of 3 m in the same time. Who has more energy and power?

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Both A and B have developed equal power but B has more energy

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Both A and B have developed equal power but A has more energy

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Open in App

Solution

The correct option is B
B

Person A: mass of body is m = 5 kg

Co-efficient of friction is μ = 0.3

Therefore, Force of friction is F = μmg = 0.3 x 5 x 10 = 15 N

Displacement is s = 4 m

Hence, Work done is W = 15 x 4 = 60 J

Time taken is t = 15 s

Hence, Power is P = 60/15 = 4 W

Person B: mass of body is m = 7 kg

Co-efficient of friction is μ = 0.3

Force of friction is F = μmg = 0.3 x 7 x 10 = 21 N

Displacement is s = 3 m

Hence, Work done is W = 21 x 3 = 63 J

Time taken is t = 15 s

Hence, Power is P = 63/15 = 4.2 W

Thus, person B has more energy and power.

Suggest Corrections

Similar questions

Q. A body is pulled through a distance of 5m on a rough surface. If the mass of the body is 5kg and

μ = 0.2

, then the heat energy developed as a result of friction is

Q. A man pushes a

10 k g

box at a constant velocity over a distance of

4 m

on a rough horizontal surface. The coefficient of kinetic friction between the box and the floor is

0.3

. Calculate the work done by the person on the box?

It takes 20 s for a person A of mass 50 kg to climb up the stairs, while another person B of same mass does the same in 15 s.Compare the (i) work done, and (ii) power developed by the persons A and B.

Q. Name the laws involved in the following situations :
(a) the sum of products of masses and velocities of two moving bodies before and after their collision remains the same.
(b) a body of mass 5 kg can be accelerated more easily by a force than another body of mass 50 kg under similar conditions
(c) when person A standing on roller skates pushes another person B (also standing on roller skates) and makes him move to the right side, then the person A himself gets moved to the left side by an equal distance.
(d) if there were no friction and no air resistance, then a moving bicycle would go on moving for ever.

Q. A body having kinetic energy

k

moving on a rough horizontal surface is stopped at a distance

x

by constant frictional force. The force of friction exerted on the body is

Join BYJU'S Learning Program