# physic

posted by .

A dynamite blast at a quarry launches a rock straight upward, and 2.0 s later it is rising at a rate of 15 m/s. Assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b)4.2 s after launch

• physic -

v = Vi - gt
when t = 2, v = 15
15 = Vi - 9.8*2
solve for Vi

then using that Vi solve for v at t = 4.2

• physic -

a. is 34.6
so would b) be v=34.6-(9.8)(4.2)

## Similar Questions

1. ### Physics

A dynamite blast sends a piece of rock (shatter) straight upwards. After 2.31x10^0 s the piece of rock has a velocity of 1.56x10^1 m/s. Assuming there is no air resistance, what is the initial velocity of the rock, to two significant …
2. ### physics

A dynamite blast at a quarry launches a rock straight upward, and 2.0 s later it is rising at a rate of 15 m/s. Assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b)4.2 s after launch.
3. ### Physics

A dynamite blast at a quarry launches a rock straight upward, and 1.5 s later it is rising at a rate of 19 m/s. Assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b)4.6 s after launch.
4. ### physics

A dynamite blast at a quarry launches a chunk of rock straight upward, and 2.0s later it is rising at a speed of 15m/s. Assuming air resistance has no effect, calculate its speed A) at launch and B) 5.0s after lauch
5. ### physics

A dynamite blast at a quarry launches a rock straight upward, and 1.9 s later it is rising at a rate of 14 m/s. Assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b) 5.6 s after launch.
6. ### physics

A dynamite blast at a quarry launches a rock straight upward, and 2.2 s later it is rising at a rate of 17 m/s. Assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b)4.4 s after launch.
7. ### physics

A dynamite blast at a quarry launches a chunk of rock straight upward, and 2.3 s later it is rising at a speed of 18 m/s. Assuming air resistance has no effect on the rock, calculate its speed at (a) at launch and (b) 5.4 s after the …