According to the law of conservation of momentum, the <u> TOTAL </u> amount of momentum of a group of objects does not change unless outside _____<u>FORCES</u>____ act on the objects.
Answer:
David
Explanation:
Because he is not on the ride with Ben and Justine
Answer:
Energy, E = 178.36 J
Explanation:
It is given that,
Mass 1, 
Mass 2, 
Mass 3, 
Height from which they are dropped, h = 1.3 m
Let m is the energy used by the clock in a week. The energy is equal to the gravitational potential energy. It is given by :


E = 178.36 J
So, the energy used by the clock in a week is 178.36 Joules. Hence, this is the required solution.