A circular crate has a weight of 3220 lb and it crashes into the wall. If the velocity of forward travel is 4 ft/s and it crachs after 2 s, determine the average impulsive force acting on the crate. Assume that the coefficient of kinetic friction between the wheels and the pavement is m_k = 0.3.

1) 2 kip
2) 4 kip
3) 5 kip
4) 9 kip

The crate of 3220 lb is moving in with the velocity of 4 ft/s and without brakes the equation can be written as

m(v_x)₁ + S F_x dt = m(v_x)²
(3220/32.2) 4 - F_w (2) = 0
F_w = 2000 lb = 2 kip

So the average impulsive force acting on the crate is F_w = 2 kip