Question

A .10 kg hockey puck is at rest. It encounters a force of 20 N for 0.2 seconds that sets it in motion. Over the next 2 seconds it encounters 0.4 Newton’s of resistance force. Finally it encounters a final force of 24 N for 0.05 seconds in the direction of motion. What is the final velocity of the hockey puck??

Answer 1

The mechanical impulse, of a force, is a vectorial magnitude that relates this force to the duration of its performance.
We have then:
I = F * delta t.
Since the impulse is a vector, we can then calculate the vector sum as:
I = ((20) * (0.2)) - ((0.4) * (2)) + ((24) * (0.05))
I = 4.4 N.s
Then, by definition:
I = delta p
I = delta m * v
I = m * delta v
I = m * (v-0)
Clearing v:
v = I / m
v = (4.4) / (0.10)
v = 44 m / s
answer:
the final velocity of the hockey puck is
v = 44 m / s