#1. a) potential b) potential c) kinetic c) kinetic
#2 Tommy: since Fg = mg = 4.5(9.8) = 44.1 N, so W = Fd (44.1)(0.5) = 22.05 J
Nancy: zero work since the textbook is motionless
Cindy: W = 30(4) = 120 J
Therefore, Cindy spent the most amount of energy, followed by Tommy then Nancy
#3
a) Fg = mg = 24(9.8) = 235.2 N
b) W = Fd = 300 (4.5) = 1350 J
c) Fg is reduced by a third so the new Fg = 235.2/3 = 78.4 N (use answer is part a)
So W = Fd = 78.4(1.4) = 197.76 J
#4
a) Since 8.2 = m (9.8/6), so m = 8.2/1.63 = 5 kg
{divide 9.8 by 6 because gravity on the moon is about 1/6 of Earth's}
b) W = Fd = 8.2(1.55) = 12.71 J
c) More energy is required since the rock weighs more (due to stronger gravity on Earth...6 times stronger!). This means that work required on Earth is 6 times that of the moon.
On Earth: W = 8.2(6)(1.55) = 76.26 J
On moon: W = 12.71 J (answer in part b)
Therefore difference in energy spent = 63.55 J
****There are different ways to solving these questions. Also, rounding may have affected certain answers so yours do not need to be an exact match to the above answers.***
