What am I doing wrong??? Question: A 41 g bullet, with horizontal velocity of 496 m/s, stops 13cm within a soid wall. What is the magnitue of the average Force from the wall stopping it? This is how i tried to solve it Vi = 496, Vf=0, and Xf-Xi=.13m So Vf^2=Vi^2+2a(Xf-Xi) Which = 0 = 246016+2a(.13) solve for acceleration you get -946215... F=m(a)...so i did (-946215)(41) which does not equal the answer? Am i doing anything wrong? 2nd Question: A girl whose weight is 264 N slides down a 5.8 playground slide that makes an angle of 20degree with the horizontal. The coefficient of kinetic friction is 0.10. If she starts at the top with a speed of 0.457 m/s, what is her speed at the bottom? This is how i tried to slove it W= change in U + change in K + change in Thermal Thermal = 143.98 (i wont show my calculations cause i am 100% sure this is righ) so.. F(d)= -mgh +(1/2)mv^2 - (1.2)m(.457^2) +143.89 After you plug in all your variables, you have two unkowns,velocity and W.. Provided i did the setup right, how do i figure out the velocity of i dont know the magnitude of her force?