Question

A 2kg block at rest is acted upon by a constant force of 20N for 4 seconds. Find: (a). what momentum is required by the block ? (b). Find the final velocity of the block. Show complete solutions.

Answer 1

a) The required momentum can be found from the second Newton's law:

$$p = F\Delta t$$

where $F = 20N, \Delta t=4s$. Thus, obtain:

$$p = 20N\cdot 4s = 80 kg\cdot m/s$$

b) The velocity can be found from the definition of the momentum:

$$v = \dfrac{p}{m}$$

where $m = 2kg$. Thus, obtain:

$$v = \dfrac{80kg\cdot m/s}{2kg} = 40m/s$$

Answer. a) 80kg*m/s, b) 40 m/s.