1. Mass affects / does not affect the conservation of energy. 2. How much potent
ID: 1393611 • Letter: 1
Question
1. Mass affects / does not affect the conservation of energy.
2. How much potential energy does the 60. kg skater have before she starts her ride, 12 m above the ground?
__________
3. How much kinetic energy does a 60.0 kg skater have traveling with a velocity of 4 m/s?
__________
4. How fast must a 20. kg skater travel to have a kinetic energy of 360 Joules?
__________
5. How high must a 2.0 kg basketball be thrown so it has a potential energy of 160 J?
__________
6. How fast must the 2.0 kg basketball be thrown upward to achieve the same 160 J?
__________
7. If a 75kg skater starts his skate at 8.0m, at his lowest point, he will have a velocity of
__________
8. In the above question, all the potential energy became kinetic energy. How much work was
done? _________
Explanation / Answer
1) U = m*g*h = 60*9.8*12 = 7056 J
2) KE = 0.5*m*v^2 = 0.5*60*4^2 = 480 J
3) KE = 0.5*m*v^2
==> v = sqrt(2*KE/m)
= sqrt(2*360/20)
= 6 m/s
4) U = m*g*h
==> h = U/(m*g)
= 160/(2*9.8)
= 8.16 m
5) KE = 0.5*m*v^2
==> v = sqrt(2*KE/m)
= sqrt(2*160/2)
= 12.65 m/s
6) v = sqrt(2*g*h)
= sqrt(2*9.8*8)
= 12.52 m/s
7) Workdone = m*g*h
= 75*9.8*8
= 5880 J
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