# Math

posted by .

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)

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
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.

• Math -

heck, they gave you the equation.

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)

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

h(3.06) = 98.9

• Math -

I don't get how you got:
vertex of any parabola is where x = -b/2a = -30/-9.8 = 3.06

h(3.06) = 98.9

where did all the numbers come from?

• Math -

how did you get t=6.12 for a)???

## Similar Questions

1. ### Algebra

THe function h(t)=-16t^2+v0t+h0 describes the height in feet above the ground h(t) of an object thrown vertically from a height of h0 feet, with an initial velocity of v0 feet per second, if there is no air friction and t is the time …
2. ### College algebra

When a ball is thrown up into the air, it makes the shape of a parabola. The equation S= -5t^2 + v*t + k gives the height of the ball at any time, t in seconds, where âvâ is the initial velocity (speed) in meters/sec and âkâ …
3. ### Math

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 I didn't …
4. ### Math Help (URGENT X10)

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 …
5. ### algebra

A ball is thrown upward with an initial velocity of 14 meters per second from a cliff that is high. The height of the ball is given by the quadratic equation H = 49t^2 + 14t +60 where h is in meters and t is the time in seconds since …
6. ### math

A ball is thrown upward with an initial velocity of 35 meters per second from a cliff that is 80 meters high. The height of the ball is given by the quadratic equation h = -49t^2 + 35t + 140 where h is in meters and t is the time in …
7. ### Algebra 1

A ball is thrown upward with an initial velocity of 35 meters per second from a cliff that is 80 meters high. The height of the ball is given by the quadratic equation h = -49t^2 + 35t + 140 where h is in meters and t is the time in …
8. ### Algebra

The height, in meters, of a projectile can be modeled by h= -4.9t^2 + vt + s where t is the time (in seconds) the object has been in the air, v is the initial velocity (in meters per seconds) and s is the initial height (in meters). …
9. ### Math

In physics, one learns that the height of an object thrown upward from an initial height of h0 feet with an initial velocity of v0 (in feet per second) is given by the formula h(t)=−16t^2+v0t+h0 feet where t is the amount of …
10. ### Maths

object thrown upward from an initial height of h0 feet with an initial velocity of v0 (in feet per second) is given by the formula h(t)=−16t^2+v0t+h0 feet where t is the amount of time in seconds after the ball was thrown. Also, …

More Similar Questions