# Math Help - Question related to g of earth

1. ## Question related to g of earth

If A ball is thrown straight up with a speed of 45 m/s. How long does it take the ball to reach its maximum height?

2. ## Re: plz help for question related to g of earth

Originally Posted by moonnightingale
If A ball is thrown straight up with a speed of 45 m/s. How long does it take the ball to reach its maximum height?
note ... the ball loses 32 ft/s of speed every second

3. ## Re: plz help for question related to g of earth

how u calculated that

4. ## Re: plz help for question related to g of earth

Well, I presume that, at some time, skeeter took a science course in which he learned that the acceleration due to gravity, at the surface of the earth, is 32 feet per second per second.

5. ## Re: plz help for question related to g of earth

Originally Posted by HallsofIvy
Well, I presume that, at some time, skeeter took a science course in which he learned that the acceleration due to gravity, at the surface of the earth, is 32 feet per second per second.
and the really amazing thing is ... I passed the course!

6. Originally Posted by moonnightingale
If A ball is thrown straight up with a speed of 45 m/s. How long does it take the ball to reach its maximum height?
u = 45 m/s

v = 0 m/s (at maximium height velocity is 0 m/s).

a = -9.8 m/s^2 (-ve because if u = +45 m/s then downwards is the negative direction).

v = u + at. Substitute the data. Solve for t.

You give no idea what you've been taught - I'm assuming you have met the uniform straightline motion formulae .....

It looks like you might need to go back and review your class notes and/or textbook.

Originally Posted by skeeter
note ... the ball loses 32 ft/s of speed every second
Correct. However, the question is using SI units ..... (which might explain the OP's follow-up question ....?)

7. ## Re: Question related to g of earth

Originally Posted by mr fantastic
u = 45 m/s

v = 0 m/s (at maximium height velocity is 0 m/s).

a = -9.8 m/s^2 (-ve because if u = +45 m/s then downwards is the negative direction).

v = u + at. Substitute the data. Solve for t.

You give no idea what you've been taught - I'm assuming you have met the uniform straightline motion formulae .....

It looks like you might need to go back and review your class notes and/or textbook.

Correct. However, the question is using SI units ..... (which might explain the OP's follow-up question ....?)
true ... thought I saw ft/s ... oh, well, it happens.

8. ## Re: Question related to g of earth

Originally Posted by skeeter
true ... thought I saw ft/s ... oh, well, it happens.
I was going to make some wise-acre comment about slugs, but nothing came to mind .....