Posted by **elaine** on Tuesday, October 19, 2010 at 8:54pm.

A stone is dropped from a 75 m high building. when this stone has dropped 15m, a second stone is thrown downward with an initial velocity such that two stones hit the ground at the same time. find a. time taken for the first stone to fall 75m. (b) the time taken for the second stone to hit the ground (c.) what as the initial velocity of the second stone

- physics -
**Henry**, Thursday, October 21, 2010 at 12:38pm
a. d = 0.5gt^2,

75 = 0.5 * 9.8t^2,

75 = 4.9t^2,

Divide both sides by 4.9:

t^2 = 75 / 4.9 = 15.3,

t = sqrt(15.3) = 3.9 s.

b. d = Vo*t + 0.5gt^2,

Vo*t = 15 m,

75 = 15 + 0.5 * 9.8t^2,

75 - 15 = 4.9t^2,

60 = 4.9t^2,

Divide both sides by 4.9:

t^2 = 60 / 4.9 = 12.2,

t = sqrt(12.2) = 3.5 s.

c. Vo*t = 15,

Vo * 3.5 = 15,

Vo = 15 / 3.5 = 4.3 m/s.

## Answer This Question

## Related Questions

- Physics - a stone is dropped from a 75m building. when a stone has dropped 15m, ...
- physics - A stone is dropped from a 75 m high building. when this stone has ...
- Physics - A stone is dropped from rest from the roof of a 100-m high building; 2...
- science - A stone is dropped into a river from a bridge 43.9 m above the water...
- physics - A stone is dropped from the roof of a building; 1.60s after that, a ...
- Physics - A stone is dropped from the roof of a building: 2.5s after, a second ...
- physics - An inquisitive physics student and mountain climber climbs a 50.0 m ...
- Physics - Hi guys, need help with this problem for physics and im having trouble...
- physics - Two stones are thrown vertically up at the same time. The first stone ...
- physics - Two stones are thrown vertically up at the same time. The first stone ...

More Related Questions