This post is focused on Numerical Problems on Work, Energy, Power with solutions, and a problem worksheet for you. This is very useful for high school students studying Physics, more precisely for class 10 students of ICSE, CBSE, international boards like IGCSE, state boards, etc.)
Numerical Problems on Work, Energy, Power | class 10 ICSE, CBSE | solved
i] Find the kinetic energy of a ball of mass 500 g moving at a speed of 20 cm/s.
mass m = 500 g = 0.5 kg
velocity v = 20 cm/s = 0.2 m/s
The Kinetic Energy is K = (1/2) . m. v2 = (1/2)(0.5)(0.2)2=0.01 J
ii] An object of mass 1 kg is raised through a height h. Its potential energy is increased by 1 J. Find the height h.
ii] Solution: The potential energy increase for a raise of height h = mgh
Here, m = 1 kg. g = 9.8 m/s2. h = ?
Therefore, (1)(9.8)h = 1
h = 1/9.8 =0.102 m
iii] A man carrying a bag of mass 25 kg climbs up to a height of 10 m in 50 seconds. Calculate the power delivered by him to the bag.
iii] Solution:The force applied by the man on the bag = weight of the bag = 25 x 9.8 N = 245 N
Height = 10 m
so the work done = W= 245 x 10 J = 2450 J
Time taken =t= 50 seconds.
So the power delivered = W/t = 2450/50 Watt = 49 Watt
iv] Calculate the work done by a man in lifting a 0.5 kg box from the ground and keeping it on a shelf 2 meter high.
m = 0.5 kg
g = 9.8 m/s2
Weight of the box = mg = 0.5 x 9.8 N = 4.9 N
The force to be applied on it upwards to lift it =F= the weight of the box = 4.9 N
Displacement along the direction of force (upwards here) = d = 2 m
So work done = Force x displacement along the line of force = F d =4.9 x 2 J = 9.8 Joule
v] A roller is pushed with a force of 100 N along its handle, which is at an angle of 60 degrees with the horizontal. Find the work done in moving it through 20 m.
W = Fd cos θ = 100 x 20 x cos 60 = 100 x 20 x (1/2)
= 1000 Joule
Work, Energy, Power Worksheet – More numerical problems to solve
1 ) A block of mass 1 kg slides down on an inclined plane of inclination 60 degrees. Find the work done by the block’s weight as it slides through 100 cm. Full Solution
2 ) A force of 20 N displaces an object through 20 cm and does work of 2 J in the process. Find the angle between the force and the displacement. Full Solution
3 ) A player kicks a ball of mass 250 g placed at the center of the field. The ball leaves his foot with a speed of 8 m/s. Find the work done by the player on the ball. Full Solution
4 ) A 1 kg ball is thrown up with a speed of 19.9 m/s. Calculate the work done by its weight in one second. Full Solution
5 ) A 10 kg ball is thrown upwards with a speed of 5 m/s. (a) Find its potential energy when it reaches the highest point. (b) Calculate the maximum height it reaches. Full Solution
6 ) A 10 kg ball is dropped from a height of 10 m. Find (a) the initial potential energy of the ball, (b) the kinetic energy just before it reaches the ground, and (c) the speed just before it reaches the ground. Full Solution
7 ) A body A of mass 3 kg and a body of mass 10 kg are dropped simultaneously from a height of 14.9 m. Calculate (a) their momenta (b) their potential energies, and (c) their kinetic energies when they are 10 m above the ground.
8 ) A block of mass 4 kg slides on a rough surface. At t=0, its speed is 2 m/s. It stops after covering a distance of 20 cm because of the friction exerted by the surface on it. Find the work done by friction.
9 ) A ball is dropped from a height H. When it reaches the ground, its velocity is 40 m/s. Find the height H.
10 ) A man does 200 J of work in 10 seconds and a boy does 100 J of work in 4 seconds. (a) Who is delivering more power? (b) Find the ratio of the power delivered by the man to that by the boy.
11 ) A cycle together with its rider weighs 100 kg. How much work is needed to set it moving at 3 m/s?
12 ) Two persons do the same amount of work. The first person does it in 10 seconds and the second, in 20 seconds. Find the ratio of the power used by the first person to that by the second person.