can you find an angle if only given the the total time and total distance?
1 Vote   • Comment on Hannah Jones's question • Flag Hannah Jones's comment about 3 hours ago by   View profile for: Hannah Jones
Well first break up the initial velocity into components:
vx = vi cos θ (velocity in x direction)
Solve for vi:
vi = vx/cos θ
We know distance and time, so vx = d/t which is a value.
So vi = (d/t) / cos θ
vy = vi sin θ (initial velocity in y direction)
Substitute vi:
vy = [(d/t) / cos θ] sin θ
a = -9.8 m/s^2 is assumed
So we have initial velocity in y direction, acceleration, and time.
We can use the kinematic equation: vf = vy + a*t. If we substitute in what we know there are still 2 unknowns, vf and θ. What to do? We need another equation...
Half the time. This is when we know vf = 0 as the object is at its maximum height:
How about now?
0 = [ (d/t) / cos θ ] sin θ + a * (t/2)
The only unknown is θ. Did we do it?? Test it on a problem that has all these variables!!
1 Vote   • Comment on Sam Woon's question • Edit • Delete 14 minutes ago by   View profile for: Sam Woon