How far does the package in Figure 7.4 coast after the push, assuming friction remains constant? Use work and energy considerations.

Data given in Figure 7.4

Strategy 

We know that once the person stops pushing, friction will bring the package to rest. In terms of energy, friction does negative work until it has removed all of the package’s kinetic energy. The work done by friction is the force of friction times the distance traveled times the cosine of the angle between the friction force and displacement; hence, this gives us a way of finding the distance traveled after the person stops pushing.

Fa 120 N app = m = 30.0 kg w N W f = 5.00 N d = 0.800 m