# Homework Help: Linear Momentum

1. Sep 29, 2011

### bionut

(Q) a 108 cm, 0.73kg golf club is swung for 0.5s with a constant acceleartion of 10 rad/s (squ). What os the linear momentum of the club head when it impacts the ball?

Known:
H= 108cm = 1.8m
m = 0.73 kg =7.16N
t = 0.5s
$\alpha$= 10 rad/s (squ)

I know momentum = mass x velcoity

So velcotiy = d/t.... (so i need to find the dispalcement)

But Im thorwn but the angular accelertion o 10 rad/s(squ)
The only thing I can think of is using 2(pi)r with r being the 1.8m?

Any sugegstion where to go from here ??

2. Sep 29, 2011

### BobG

If you were talking about linear motion, you could find your linear velocity using your linear acceleration.

$$v_f=v_i + at$$

Same principles apply to rotational motion, except now you're looking at:

$$\omega_f = \omega_i + \alpha t$$

3. Sep 29, 2011

### bionut

Hi.. thanks what you have said makes sense...

But is I use:

wf=wi + at

wf= 0 + 10 X 1.5

The linear momentum = mv = 0.73 x 5 = 3.65 kg. m/s

But the answer is 3.9 kg. m/s, I know im only .25 off but is the book wrong or my calculations wrong ??

4. Sep 30, 2011