Physics questions

anpanman SG

Hello,

1. A bullet of mass 4.0g is fired at a speed of 0.60 km s-1 into a ballistic pendulum of mass 1.0kg and thickness 0.25m. The bullet emerges from pendulum with speed of 0.10 km s-1. Calculate

a) average retarding force acting on the bullet in its passage through the block

Taking rightwards as +ve

Change in momentum of bullet = (4/1000) (100-600) = -2 Ns (righwards)

By Newton's 2nd law,

Force exerted on bullet in passage through block = 2 N (Pls help me check if my statements are valid)

b) speed of the pendulum after the bullet emerges from it

I got 2 m s-1 using the formula for conservation of momentum

C) the height to which the pendulum rises. (not sure how to solve this, pls do help)

Thanks

eagle SG

Hi, you might want to try this question too before you attempt part c again:

http://examworld.blogspot.com/2008/12/lvl-h2-phy-dynamics.html

Your answer to (a) is wrong because Force is change in momentum over time. The time taken to go through the pendulum isn't 1 s!

To solve it, you have to use v^2 = u^2 + 2as, where s = 0.25m
Then find a

b) Right

c) try to do the question in my link first