A rubber ball is shot straight up from the ground with a speed of 12 m/s. Simultaneously, a second identical rubber ball is dropped from rest exactly 7 m directly above the first ball. At what height (in m) do the two balls collide?

6.17 m

Explanation:

We are given that

Initial speed of rubber ball, u=12 m/s

Total height, h=7 m

Initial speed of second ball, u'=0

We have to find the height at which the two balls collide.

Let  first rubber ball and second ball strikes after t time.

For first ball

Distance traveled by first ball in time t

Substitute the value

  ...(1)

Distance traveled by second ball in time t

 .....(2)

Using equation (2) in equation (1) we get

sec

Now, using the value of t

S=6.17 m

Hence, at height 6.17 m the two balls collide .

when insulating materials rub against each other, they may become electrically charged . electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. the material that gains electrons becomes negatively charged. the material that loses electrons is left with a positive charge.

the answer is b, have negligible mass