63.1 N

1
A 15 kg cart is going 12 m/s at the bottom of a
2.15 m tall hill. At the top, it hit its brakes
for a distance of 4.5 m, and is going 8.0 m/s
after this. What force do the brakes exert?
15 kg
h 2.15 m
Vi 5.8 m/s
Fd mgh 1/2mv2 Fd mgh 1/2mv2 0
mgh 1/2mv2 0 0 1/2mv2 1/2(15
kg)(12 m/s)2 (15 kg)(9.8 N/kg)(2.15 m) F(4.5
m) 1/2(15 kg)(8.0 m/s)2
W
63.1 N