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?

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