Question

What is an example of an impulse practice problem?

Answer 1

First of all, using the definitions `a = (dv)/(dt)` and `F = ma`, the definition of impulse is:

`I = intFdt = int madt = m int(dv)/cancel(dt)cancel(dt)`

`I = m intdv`

`I = mDeltav`

...whereas `p = mv`

Thus, an impulse causes an object to change velocity as a result of an impact. Or, it can be said that it is summation of the infinite instances of instantaneous force applied over a small amount of time.

A nice example is right when a golf club hits a golf ball. Let's say there was a constant impulse for `0.05 s` on a golf ball started at rest. If the golf ball is `45 g` and its velocity after it leaves contact with the golf club is `50 m/s`, what was the impulse?

`I = mDeltav`

`I = (0.045 kg)(50 m/s - 0 m/s) = 2.25 kg*m/s`

The average force applied onto the golf ball in these `0.05` seconds would be what?

`F_(avg) = 1/Nsum_(i=1)^NF_i = (FDeltat)/(Deltat) = I/(Deltat) = (2.25 N*s) / (0.05 s) = 45 N`

And I'll leave this one for you:

If the golf ball leaves the tee at a `45^o` from the horizontal, how long does it take for it to cross the spot that lines up horizontally with its initial position?