Скачать или смотреть Fan cart: work, power, impulse and average force for a fan cart accelerated from rest.

00:00 Given the time and final speed for a fan cart accelerated from rest, we have four questions to answer about work, power, impulse and average force.

00:15 Compute the total work done by the fan on the cart. For the fan cart, work is computed by simply observing the final kinetic energy of the fan cart. Since the cart started from rest, the final kinetic energy all came from the work done by the fan on the cart. So, we compute the final kinetic energy 1/2*m*v^2, and we arrive at a number for the work done by the fan.

00:40 Next, we compute the average power output of the fan. Average power is just the rate at which work is done, so we divide the total work done by the time it took to do the work, and we arrive at an answer for the average power output of the fan for the accelerating cart.

01:00 Compute the impulse delivered by the fan. Impulse is simply the change in momentum, and we know the initial momentum is zero. Thus, the impulse is just the final momentum. We plug into p=mv and arrive at an answer for the impulse delivered to the cart.

01:31 Compute the average force on the cart exerted by the fan. Average force is the time rate of change of the momentum F=delta(p)/delta(t), so we divide the impulse by the time for the process and arrive at an answer for the average force on the cart. Bonus: we show that the units in our answer are Newtons by referring back to Newton's second law.