1. Mike wears an 8.50 kg backpack while scaling a cliff. After 90 minutes, Mike is 11.2 m above the starting point. a. How much work does Mike do on the backpack?
b. If Mike weighs 630 N, how much work does he do lifting himself and the backpack?
c. What is the average power developed by Mike?

a. 952Joules

b. 8008 joules

c. 1.48 watts

i would say the answer is food.

hope this !

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me