Question

A boy and his bicyclehave a total mass of 40 kg. at the top of the hill his speed is 5ms -1 and his speed doubles at the bottom of the hill. The hill is 10 metre height. Calculate

a)the total energy at the top of the hill
i) 4000 J
ii) 4500 J
iii) 5000 J
iv) 5500 J

b) the total energy at the bottom of the hill
i) 20000 J
ii) 22500 J
iii) 25000 J
iv) 27500 J

c) the energy lost due to friction ​
i) 1500 J
ii) 2000 J
iii) 2500 J
iv) 3000 J

Answer 1

The total energy at the top of the hill is 3920 J, the total energy at the bottom of the hill is also 3920 J, and no energy is lost due to friction.

Step-by-step explanation:

Given that the total mass of the boy and the bicycle is 40 kg, and the hill has a height of 10 meters, we can calculate the total energy at the top and bottom of the hill using the gravitational potential energy formula:

PE = mgh

At the top of the hill, the boy's speed is 5 m/s. The total energy at the top of the hill is therefore:

PE top = mgh = 40 kg * 9.8 m/s^2 * 10 m = 3920 J.

At the bottom of the hill, the boy's speed doubles to 10 m/s. The total energy at the bottom of the hill is:

PE bottom = mgh = 40 kg * 9.8 m/s^2 * 10 m = 3920 J.

The energy lost due to friction can be calculated by subtracting the total energy at the bottom of the hill from the total energy at the top of the hill:

Energy lost = PE top - PE bottom = 3920 J - 3920 J = 0 J.