# Homework Help: Trajectory, where it will land.

1. Sep 10, 2007

### fender24

1. The problem statement, all variables and given/known data
a projectile is shot from the edge of a cliff 125m above ground level with an initial speed of 105m/s at an angle of 37 degrees with the horizontal axis.
1.determine the time taken by the projectile to hit ground.
2.determine the range X of the projectile as measured from the base of the cliff.
3.find the horizontal and verticle components of its velocity.
4.find the magnitude of the velocity
5.the angle made by the velocity vector with the horizontal

2. Relevant equations
R=(Vo^2sin2(theta))/g

3. The attempt at a solution
1.
Vf=Vo+at
0=63.19m/s+-9.8m/s^2t
-63.19m/s=-9.8m/s^2t
t=6.45s thats the time for the projectile going up the Y axis

y=125+ 63.19m/s(6.45s)+-4.9(6.45s)^2
y= 328m

d=1/2(a)(t)^2
328 = 4.9t^2
t^2=66.94
t=8.18s time going down the Y axis

time total=8.18s+6.45s=14.63s

2.
Dx=v*t
Dx=83.86m/s*14.63s
Dx=1226.87m

3. sin(37)(105m/s)=63.19m/s y
cos(37)(105m/s)=83.86m/s x
4.
5.

as you can tell, I need a lot of help in completing this problem.

Last edited: Sep 10, 2007
2. Sep 10, 2007

### Astronuc

Staff Emeritus
http://hyperphysics.phy-astr.gsu.edu/hbase/traj.html

Look for "Where will it land?"

Look at the equations of motion for x(t) and y(t).

vx is constant if one neglects air resistance, but vy will vary in time (or height) because of the deceleration due to gravity and the acceleration once the projectile reaches maximum height.

What are v0x and v0y in terms of v0 and the angle with respect to the horizontal axis?