Posted by **Paul** on Monday, August 6, 2012 at 9:14pm.

The acceleration of an object g = -9.8 m/s^2. From the top of a building of 245 m., an object is thrown upwards at an initial velocity of 12m/s

(a) What is the function for the velocity of the object?

I put vf^2 = Vi^2 + 2a(yf-yi)

vf^2 = 216.09 + 19.6 (yf - 245)

(b) Determine the function for the position of the object relative to the ground.

I don't know what to put for this one

(c) How long will it take for the object to reach maximum height?

I know that for maximum height velocity = 0 with the formula: Y = Yo + Vot+ 1/2at^2, but the problem is that when I try to isolate t, I still have the t from Vot which I don't know where to put, so I'm left with t = squ(2(Yo + Vot - Y))/a

(d) What is the velocity of the object once it reaches the ground?

For this one I'll use the same formula as for (a) but will my initial height be the maximum height reached from (c)?

- Math -
**Reiny**, Monday, August 6, 2012 at 10:25pm
my equation would be

s(t) = -4.9t^2 + 12t + 245

v(t) = -9.8t + 12

at the maximum height, v = 0

-9.8t + 12 = 0

t = 12/9.8 = 1.22 seconds

when it hits the ground, s(t) = 0

-4.9t^2 + 12t + 245 = 0

or

4.9t^2 - 12t - 245 = 0

using the formula ...

t = 8.4 or a negative

so at 8.4 seconds, v(8.4) = -9.8(8.4) + 12 = -70.32 m/sec

- Math -
**Robert**, Monday, August 6, 2012 at 10:39pm
so for (a) you used Y = Yo + Vot+ 1/2at^2 so when you derive it, you get time for the other ones, got it. THanks a lot Reiny

## Answer This Question

## Related Questions

- Physics - One object is thrown straight up at 54.9 m/s from the ground at the ...
- math - an object is thrown upward from the top of a 80-foot building with a ...
- Math - An object is thrown from the top of an 80 foot building with an initial ...
- Math3(Reiny Please Help) - An object on Earth falls with an acceleration of a=9....
- Physics - **I JUST NEED THE STEPS ON HOW TO SOLVE THE PROBLEMS** An object ...
- calculus - use a(t) = -32 ft per second squared as the acceleration due to ...
- physics - object a does a freefall motion from an 80-m building and object b ...
- math - An object is thrown or fired straight upwards at an initial speed of v_0 ...
- math - An object is thrown or fired straight upwards at an initial speed of v_0 ...
- Applied Calculus - Suppose that an object is thrown down towards the ground from...

More Related Questions