Need help with physics 201 Projectile motion
Stuck on this one problem with projectiles,
The question goes: A hobby rocket reaches a height of 72.3 m and lands 111 m from the launch point with no air
resistance. What was the angle of launch?
Assuming
max height (deltaY): 73.2
max distance (deltaX): 111
Ive tried the sin(a)/A=sin(b)B approach but didnt take long till i figured that wasnt relevant. Any help on how to approach this problem?
P.S: Wasnt there a homework help section in the forums?
February 24, 2014
9 Comments • Newest first
At max height you know V_y = 0
Without air resistance, V_y = V*sin(theta) - g*t; at max height V*sin(theta) = g*t
You also know d_y = V*sin(theta)*t - 1/2*g(t^2), and d_y is given.
You know d_x, which has no gravity or air resistance so d_x = V*cos(theta)*t_2 where t_2 = 2t due to parabolic motion; it becomes d_x = V*cos(theta)*2t with d_x given
Obviously I didn't give the answer at all, but if you can understand those equations, you have 3 unknowns (V, theta and t). The system can therefore be arranged to solve for any/all 3.
I'll post it in a bit.
It's easier with energy.
[quote=monkey3842]@EpikSnow: are you given a velocity?[/quote]
No, this is all the info. If i was given velocity i would assume my sin approach (mentioned above) Wouldve worked.
@EpikSnow: are you given a velocity?
Edit : Forget this. Taking too much time.
@monkey3842 @ness the answer is 69.0 degrees but i want to know how it got there.
[quote=Ness]You can't do that because parabolic motion and gravity.[/quote]
oh yea forgot about that
[quote=monkey3842]Not sure if that works or not but can you just divide the distance of 111m by 2 and draw a triangle starting from the starting point to the max height at 72.3 before it starts dropping down. Then use tangent to find out the angle which is tan(theta)=73.2/55.5 which gives you 52.8 degrees?[/quote]
You can't do that because parabolic motion and gravity.
Not sure if that works or not but can you just divide the distance of 111m by 2 and draw a triangle starting from the starting point to the max height at 72.3 before it starts dropping down. Then use tangent to find out the angle which is tan(theta)=73.2/55.5 which gives you 52.8 degrees?