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 i
t 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
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