View Full Version : Projectile motion help...
gigglez3576
May 4, 2011, 01:02 PM
A stone thrown at an angle in such a way that the horizontal component of its initial velocity is 20 m/s and the vertical component of its initial velocity is 40 m/s. How far does the stone travel before landing? How high does the stone travel before landing?
When I calculated the time I got 4.08 s
From that I got that the distance traveled in the x direction was 81.63
For the height I got 163.27 Did I do this correctly?
ebaines
May 4, 2011, 02:09 PM
When i calculated the time i got 4.08 s
Not quite - that's the time for the stone to reach its maximum height. It will take another 4.08 second to fall back to the ground. This comes from this formula:
d = d_0 + v_0 t + \frac 1 2 a t^2
where
d = 0\\
d_0 = 0\\
v_0 = 40 \frac m s\\
a = -9.8 \frac m {s^2}
and solve for t.
From that i got that the distance traveled in the x direction was 81.63
No, you need to fix the value for total time.
For the height i got 163.27 Did i do this correctly?
No - not sure how you got that result. The max height can be found in a couple of ways. You can use
d = d_0 + v_0 t + \frac 1 2 a t^2
and set d_0 = 0, v_0 = 40 m/s, and t = 4.08 s. Or you can use
v_2^2 - v_1 ^2 = 2ad
where v_2 = 0 ,\ v_1 = 40 m/s, and solve for d.
gigglez3576
May 5, 2011, 10:12 AM
Ok so I redid the problem and I got t equal to 9.79 seconds is that correct?
Unknown008
May 5, 2011, 10:32 AM
No, could you show how you got that time please?