Question

An unknown force accelerates a 6500kg moving van from -3m/s to -13m/s in a time of 2s. In Newtons, how large is the force?

Answer 1

By definition, the acceleration is:

$$a = \dfrac{v_f-v_i}{t}$$

where $v_f = -13m/s$ is the final velocity, $v_i = -3m/s$ is the initial velocity, $t=2s$ is the time of acceleration.

According to the second Newton's law, the force acting of the van is then:

$$F = ma = m\dfrac{v_f-v_i}{t}$$

where $m = 6500kg$ is the mass. Thus, obtain:

$$F=6500\cdot\dfrac{-13-(-3)}{2} = -52000N$$

Answer. 52000 N.