Posted by **steve Alexander** on Friday, October 24, 2008 at 7:24pm.

an object is fired upward at the end of the burn it has an upward velocity of 245m/s and is 14.7 m high

a) find the maximum height and when it is attained

b) when it reaches the ground

i know that i have to use the quadratic function s= -4.9tē+Vot+h

but for what i have the 4.9tē how can i use it and can help me with the problem please

- calculus -
**bobpursley**, Friday, October 24, 2008 at 7:30pm
For the max height, energy thinking

top PEnergy = intial PE + Initial Kenergy

mgh=mg*14.7 + 1/2 m 245^2

solve for h, the maximum height.

when is it attained?

h=14.5+245t -1/2 g t^2 for h max, solve for time t.

when it reaches the ground?

h=0 solve for time.

- calculus -
**Reiny**, Friday, October 24, 2008 at 7:40pm
The 4.9 is a fixed constant and deals with the force of gravity on earth.

Your equation would be

s = -4.9t^2 + 245t + 14.7

take the derivative set it equal to zero and solve for t

put that t back into the equation to find the maximum height

b) when it hits the ground, s = 0

so solve 0 = -4.9t^2 + 245t + 14.7 for t

- calculus -
**Anonymous**, Saturday, October 6, 2012 at 3:41am
great job

## Answer this Question

## Related Questions

- physics - A rocket moves straight upward, starting from rest with an ...
- physics - A rocket moves straight upward, starting from rest with an ...
- math - If an object is fired upward from the top of a tower at a velocity of 80 ...
- AP Calculus - A projectile fired upward from ground level is to reach a maximum ...
- Physics - A test rocket is launched vertically from ground level (y=0m), at time...
- Physics - A bullet is fired vertically upward with an initial velocity of 98m/s ...
- Algebra 2 HELP plz - An object is launched upward with an initial velocity of 64...
- algebra - A ball is thrown upward from a height of 240 feet. the height h of the...
- math - If a ball is thrown directly upward with a velocity of 80ft/s, its height...
- calculus - Can some explain how to do this problem? I tried using derivatives...