Projectile Motion

by srabi001
Tags: motion, projectile
srabi001 is offline
May30-11, 05:11 PM
P: 3
A projectile is fired from ground level at time t = 0, at an angle theta with respect to the horizontal. It has an initial speed v_0. In this problem we are assuming that the ground is level.

a) Find the time t_H it takes the projectile to reach its maximum height.
Express t_H in terms of v_0, theta, and g (the magnitude of the acceleration due to gravity).

b) Find t_R, the time at which the projectile hits the ground.

I understood the first part ti be (v_0sin(theta))/g because it took the equation to V_y =v_0sin(theta) - gt and solved for t.

Now when looking through my textbook, I found that the answer for part b is exactly the same as part a, except multiplied by 2. Can someone explain to me why its multiplied by 2? I figured since its the part after when v_y = 0 aka the peak of the ball, could you just add the t after with the t before the peak?
Phys.Org News Partner Science news on
Lemurs match scent of a friend to sound of her voice
Repeated self-healing now possible in composite materials
'Heartbleed' fix may slow Web performance
ckutlu is offline
May30-11, 05:24 PM
P: 33
The fact that t_flight equals to 2*t_peak (time taken for particle to reach its peak height) is usually made in simple projectile motion problems (When particle is dropped after flight to the same level as it was thrown)

I guess you can prove it yourself by finding the expressions for its peak height. Then only thing you should do is to consider the particle's starting point is that height and it is thrown to the ground horizontally with a velocity of v0*cos(theta).
srabi001 is offline
May30-11, 06:41 PM
P: 3
Alright cool. I think I get it now. Thanks for your help

Register to reply

Related Discussions
projectile motion/ Half projectile motion (falling from height with horizontal veloc) Introductory Physics Homework 1
Need help in a Basket Ball game(Projectile Motion / motion under Gravitation) Programming & Computer Science 1
projectile motion. how long does it take for the projectile to git the ground? Calculus & Beyond Homework 4
Projectile Motion assignment - Building a projectile launcher Introductory Physics Homework 3
Uniform Circualr Motion with Projectile Motion problem (Extremely confusing): Introductory Physics Homework 4