Physics Textbook Questions: Kinetic Energy & EPE (pg 13)

a) i) 500kg x 12m/s x 12m/s = 72,000J
ii) 0.44kg x 20m/s x 20m/s = 176J

b) 72,000 x 2 = 144,000J
144,000J / 500kg = 288m/s
Square root 288m/s = 16.97... = 17m/s

a) i) When the catapult is stretched, the EPE store increases but the GPE decreases as it is pulled downwards.
ii) When the catapult is released, the EPE store decreases and the kinetic energy of the object increases, as does the GPE, which slowly converts the kinetic into GPE.

b) i) 2N x 5m = 10J
ii) 10J / (2N / 10) = 50m/s
Square root 50m/s = 7.07...m/s = 7m/s

a) 360,000J / 100m = 3,600N

b) 360,000J / (30m/s x 30m/s) = 400kg

1/2 x 250N/m x 0.21m x 0.21m = 5.5125J = 5.5J