Question

¤While jumping for a bird your cat falls off your apartment building 45 meters high (but lands in a soft pile of marshmallows of course). ¤1) How long did it take to fall? ¤2) How fast is he going when he reaches the bottom?

I dont remember which formulas were used for how long something falls and for speed.

Answer 1

A....pile of marshmallows....!

Explanation:

I would suppose the vertical (downwards) initial velocity of the cat equal to zero (`v_i=0`); we can start using our general relationship:
`v_f^2=v_i^2+2a(y_f-y_i)`
where `a=g` is the acceleration of gravity (downwards) and `y` is the the height:
we get:
`v_f^2=0-2*9.8(0-45)`
`v_f=sqrt(2*9.8*45)=29.7m/s`
This will be the velocity of "impact" of the cat.

Next we can use:
`v_f=v_i+at`
where `v_f=29.7m/s` is directed downwards as the acceleration of gravity so we get:
`-29.7=0-9.8t`
`t=29.7/9.8=3s`