Physics Textbook Questions: GPE (pg 11)

a) As the ball falls, it loses GPE and gains an equal amount of kinetic energy. When it hits the floor, some heat and kinetic energy is lost, so when it rebounds it has kinetic and GP energy, but not as much, this starts as kinetic and becomes GPE as it nears the top of its rebound.

b) i) (1.4N x 2.5m = 3.5J) - (1.4N x 1.7m = 2.38J)= 1.12J lost
ii) Friction, Sound

a) 450N x 0.2m = 90J

b) 90J x 50 = 4500J

a) 25kg x 9.8N/kg x 1.8m = 441J

b) 1.8m - 0.3m = 1.5m
1.5m x 9.8N/kg x 25kg = 367.5J
441J - 367.5J = 73.5J

The chemical energy in someone's muscles is used as heat as your hand may be warm from friction from the object or your arm may get tired and sweat or radiate some heat. There is also work being done against gravity to keep your arm out in front of you instead of by your side and lower.