a. A 15 k g child slides down a 3.8- m -high playground slide. She starts from r

Question

a. A 15 kg child slides down a 3.8-m-high playground slide. She starts from rest, and her speed at the bottom is 1.8 m/s. What is the change in the thermal energy of the slide and the seat of her pants?

b. A 46 g marble moving at 1.9 m/s strikes a 22 g marble at rest. Assume the collision is perfectly elastic and the marbles collide head-on. What is the speed of the first marble immediately after the collision? What is the speed of the second marble immediately after the collision?

c. 16 J of heat are removed from a gas sample while it is being compressed by a piston that does 26 J of work. What is the change in the thermal energy of the gas?

Explanation / Answer

Question 1) From the conservation of energy

Initial potential energy = kinetic energy+ thermal energy (heat)

So,

mgh = mv^2/2 + heat

heat = mgh - mv^2/2

Given, m = 15 kg , h = 3.8 m , v = 1.8 m/s

So,

Heat = 15*9.8*3.8 - (15*1.8^2/2)

Heat = 534.3 joules

Therefore, thermal energy = 534.3 joules

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