# physics

posted by
**y912f**
.

please tell me if these are correct

A track star in the long jump goes into the jump at 12 m/s and launches herself at 20.0 deg above the horizontal. What is the magnitude of her horizontal displacement?

(Assume no air resistance and that Ay= -g = -9.81 m/s^2)

i got 9.2 m

There are 6 books in a stack, and each book weighs 5 N. The coefficient of static friction between the books is 0.2. With what horizontal force must one push to start sliding the top 5 books off the bottom one?

i got 3N

A rock is thrown straight upward with an initial velocity of 9.6 m/s in a location where the acceleration due to gravity has a magnitude of 9.81 m/s^2. To what height does it rise?

i got 4.7

can you please show me how to solve for this last one

thanks