Acrane is used to swing a 450 kg wrecking ball into a 500 kg wall. the crane takes 5 s to push the ball into the building. the crane provides 2000 n of force. the ball is left moving 10 m/s after the collision. how fast is the wall moving afterwards? * how does the kinetic energy change in the crane problem? 1. ke increases 2. ke decreases 3. ke stays the same what type of collision is this? elasti inelastic

This is a momentum problem, so let's find the velocity of the ball initially. It can be given by:

Let's plug in values and solve for a:

Now, we can multiply by time to get velocity:


We have all the information we need, so let's set up an equation to solve for the velocity of the wall after the collision:


Solve for velocity of wall finally:


Plug in all values:


So, the final velocity of the wall will be 10.98 m/s.
The KE in this problem initially was 110889 J (1/2mv^2). After the collision it was 52640.1 so, the KE decreased. 
Since there was no mashing of objects together, this was an elastic collision.

The definition of average speed is

        (total distance covered) divided by (time to cover the distance) .

If you didn't remember that, you can still solve the problem
if you Use your units !

You want a number that has units of  [ mile / minute ].

That's what you get if you divide the miles by the minutes.

         Average speed  =  (15 miles)  /  (70 minutes)

                                     =       ( 15 / 70 )   miles/minutes

                                     =          0.214 mile / minute  (rounded)