# physics

posted by .

Two balls are dropped, one from height H and the other from a height of 4H. How far apart should they be dropped (time wise) to hit the ground at the same time.

• physics -

h=1/2 g t^2 is the basic formula.

H=1/2 g (t-to)^2 where to is the time the lower one is dropped, after the higher.
4H=1/2 g t^2
So, both balls hit at time t.

t=sqrt 8H/g
H=1/2 g (sqrt(8H/g)-to)^2
2H=g(8H/g-2to*sqrt(8H/g)+to^2)

to^2-2to* sqrt(8H/g)-2H/g

a=1 b=-2sqrt(8H/g) c= -2H/g

## Similar Questions

1. ### Physics

A mass is dropped from a height of 30m, and at the same time from ground level (and directly beneath the dropped mass), and another mass is thrown straight up with a speed of 15 m/s. a) How far apart are the two masses after 0.5 s?
2. ### physics

A mass is dropped from a height of 30m, and at the same time from ground level (and directly beneath the dropped mass), and another mass is thrown straight up with a speed of 15 m/s. a) How far apart are the two masses after 0.5 s?
3. ### physics

A mass is dropped from a height of 30m, and at the same time from ground level (and directly beneath the dropped mass), and another mass is thrown straight up with a speed of 15 m/s. a) How far apart are the two masses after 0.5 s?
4. ### physics

How many secons apart should two balls be released so that a ball being deopped from a height of H reaches the ground at the same time as a ball dropped from a height of 5H?
5. ### physics

two balls are dropped to the ground from different heights. one ball is dropped 2s after the other but they both strike the ground at the same time, 5s after the first is dropped. what is the difference in height from which they are …
6. ### Physics

Two balls are dropped from rest from the same height. One of the balls is dropped 1.0 s after the other. What distance separates the two balls 2.00 s after the second ball is dropped?
7. ### science

A class is learning about acceleration due to gravity. Their plan is to climb a ladder and drop different kinds of balls from the same height at the same time. They will repeat this for ten trials, recording the data after each test. …
8. ### PHYSICS

A BALL IS DROPPED A HEIGHT AT THE SAME TIME AS ANOTHER BALL IS PROJECTED HORIZONTALLY FROM THE SAME HEIGHT. 1.WILL THE BALLS HIT THE GROUND AT THE SAME TIME. 2.EXPLAIN YOUR ANSWER IN (1).
9. ### Physic

A ball B1 is dropped from the top of a building, one second later another ball, B2 is thrown down with an initial speed of 20.0m/s. The two balls hit the ground at the same time. 1)What is the time it took B1 to teach the ground?
10. ### Pre calculus

When “superballs” sprang upon the scene in the 1960’s, kids across the United States were amazed that these hard rubber balls could bounce to 90% of the height from which they were dropped. If a superball is dropped from a height …

More Similar Questions