Homework Help: Math Help (URGENT X10)

Posted by Anonymous on Wednesday, April 4, 2012 at 10:42pm.

This is really urgent so please please please help.

The height(H) of an object that has been dropped or thrown in the air is given by:
H(t)=-4.9t^2+vt+h
t=time in seconds(s)
v=initial velocity in meters per second (m/s)
h=initial height in meters(m)

H=height
h=initial height
Is there a difference but, anyway I didn't make this clear on the last post.

A ball is thrown vertically upwardd from the top of the Leaning Tower of Pisa (height=53m) with an initial velocity of 30m/s. Find the time(s) at which:
a)the ball's height equals the hight of the tower
H(t)=-4.9t^2+30t+53
H(t)=???

b)the ball's height is greater than the height of the tower

c)the ball's height is less than the height of the tower

d)the ball reaches its maximum height

I don't know how to do this problem.

Please Help and Thank You very much =)

Math Help (URGENT X10) - Rami Dahabreh, Thursday, April 5, 2012 at 2:15am
acceleration downward due to gravity is 10m/s to be exact 9.8m/s
this is enough to get you to start thinking
Math Help (URGENT X10) - Steve, Thursday, April 5, 2012 at 11:04am
h(t) = -4.9t^2 + 30t + 53

a) ball goes up, comes back down to the top of the tower. So, we want

53 = -4.9t^2 + 30t + 53
0 = -4.9t^2 + 30t
0 = t(-4.9t + 30)
so, t=0 (at the start) or t = 6.12 (as it comes back down)

If t(-4.9t+30)=0, either
t=0
or
-4.9t+30 = 0
That is, t = 6.12

If you can't solve a factored expression, you have some review to do.

b) same calculation but, t is between 0 and 6.12. That is 0 < t < 6.12

c) same calculation, but restricting t to positive values, t>6.12
Naturally, we could also restrict t to the point where height >= 0.

d) vertex of any parabola is where x = -b/2a = -30/-9.8 = 3.06

you know from the quadratic formula that x = -b/2a ą sqrt(blah blah)
Parabolas are symmetric, so the vertex is midway between the roots, which are equally spaced around x = -b/2a

h(3.06) = 98.9

Answer this Question

Related Questions

GEOGRAPHY (URGENT!!!) - I NEED HELP!!! this is urgent!!! Human-Environmental ...
Physics please help - A small circular object with mass m and radius r has a ...
Literature - Can someone help me on this? its really urgent. what is Foil ...
spanish!!...urgent!...please help - how did the geography influence the ...
GR.10 CIVICS!!!!!URGENT - CAN SOMOENE PLEASE GIVE ME A LINK TO A PICTURE THAT ...
Math please help! Urgent - Find the height of an equilateral triangle with ...
Physics - urgent, please help! - 10pm. I asked "Show mathematically that to...
Trigonometry Urgent! - I am writing a paper on the 8 trigonometric identites but...
math help - Thank you for helping me with the last problem Reiny and Bosnian. ...
math URGENT - please factor 2.75x^2-7x-120

For Further Reading

First Name:
School Subject:
Answer: