The Physics Problem Solver/Mechanics/Momentum and Conservation of Momentum

A block of mass m = 3.5 kg, moving on a frictionless surface with an initial speed Vo = 5.4 m/s, makes a perfectly elastic collision with a block of mass M at rest. After the collision, the 3.5 kg block recoils with a speed of V = 0.4 m/s. In Figure 8.2, the blocks are in contact for 0.20 s. The average force on the 3.5 kg block, while the two blocks are in contact, is closest to: