# Find initial Velocity with only distance, angle, and acceleration.

1. Oct 9, 2009

### Jimkatz809

1. The problem statement, all variables and given/known data
A cannon sends a projectile towards a target
a distance 1580 m away. The initial velocity
makes an angle 24◦ with the horizontal. The
target is hit.
The acceleration of gravity is 9.8 m/s2 .
What is the magnitude of the initial veloc-
ity?

How high is the highest point of the trajec-
tory?

How long does it take for the projectile to
reach the target? (Assume no friction)

2. Relevant equations

3. The attempt at a solution

2. Oct 9, 2009

### rl.bhat

Collect the relevant equations for projectile motion from any source.

3. Oct 9, 2009

### Jimkatz809

Ive spent about 2 hours trying and trying this problem but i can't figure out the answers.
The equations i used were
Vox=VoCos0o
Voy=VoSin0o
V^2=Vo^ plus 2a(x-xo)
V=Vo plus at

4. Oct 9, 2009

### rl.bhat

Since there is no acceleration in the x direction, vox remains constant.
Using the last equation you can find the time to reach the maximum height. Here V = 0, Voy = Vosinθ and a = g.
Double that time is the time of flight t.
Range of the projectile R = Vo*cosθ* t

5. Oct 9, 2009

### Jimkatz809

Vo is not given

6. Oct 9, 2009

### rl.bhat

First of all find t in terms of Vo, sinθ and g. substitute this value in the expression for R and solve for Vo.