# Physics

posted by .

A particle of mass m is shot with an initial velocity vector v i and makes an angle θ with the horizontal, as shown below. The particle moves in the gravitational field of the Earth. (makes a shape of a parabola)Find the angular momentum of the particle about the origin when the particle is at the following locations. (Use v_i for vi, theta for θ, m, and g as appropriate in your equations.)
Known equations:
L=r x p ====> r x mv
a)m(v_i)(sin(theta))
b) ?
c)v_i^2( sin2(theta))/g * v_i sin(theta)

Thank you I appreciate your help!

• Physics -

You do not provide or describe the figure.
You do not identify "the following locations"
You do not tell us what parts (b) and (c) of the question are.

Your answer to (a) does not have the correct dimensions for angular momentum, and therefore cannot be right.

It is not possible to provided assistance because of these omissions

• Physics -

My apologies

The "following locations"
a) at the origin
b)at the highest point of its trajectory
c)just before it hits the ground

the dimensions of angular momentum: ? kg*m^(2)/s

the picture is simply a parabola, a projectile launched with some angle theta with respect to the horizontal

• Physics -

and for part a I realized that it is 0 because the particle is at the origin and I have to find the angular momentum of the particle about the origin:
a = vi x= r
r = 0

• Physics -

emath:
Thank you for taking the time to clarify and complete your question. Your answer to part (a) is correct.
There is a shortcut you can take for calculating the angular momentum with respect to the origin. Write the position in vector form as r = x i + y j, and the momentum as
p = m Vx i + m Vy j. The cross product is then
r = p x r = m(Vx*y - Vy*x) k
(k is a unit vector perpendicular to i and j . 'i' is horizontal along the path and 'j' is vertical.

Next, write down the equations for x, y, Vx and Vy in terms of t

x = Vi cos theta * t
y = Vi sin theta * t - (g/2) t^2
Vx = Vi cos theta
Vy = Vi sin theta - gt

L = m [Vi^2 sincos theta *t -Vi cos theta *t - Vi^2 sincos theta *t + Vi cos theta * g t/2]

At t=0, L obviously = 0, in agreement with your result

For parts (b) and (c) of your question, calculate the corresponding t and then calculate L using the equation above.

For example, at the top of the trajectory, t = (Vi sin theta)/g
At the end of the trajectory, t is twice that amount.

The resulting equation will look a bit messy. I leave the final steps to you

• Physics -

Hey drwls, can you go ahead and finish the rest of the equations, please? I'm having much difficulty with the final equation.

## Similar Questions

1. ### physics

The three forces shown in the figure below act on a particle (with F1 = 48.0 N, F2 = 58.0 N, θ1 = 63.0°, and θ2 = 27.0°). If the particle is in translational equilibrium, find F3, the magnitude of force 3 and the angle …
2. ### physics

Several forces act on a particle as shown in the figure below (where F1 = 75.0 N, F2 = 65.0 N, θ1 = 25.0° and θ2 = 74.0°, . If the particle is in translational equilibrium, what are the values of F3 (the magnitude of force …
3. ### physics

Particle A of mass 'm' has initial velocity v.After colliding with a particle B of mass'2m' the particles have the following paths B makes an angle 45 degree while A makes an angle X.first,A was moving straight.Find X.
4. ### angular momentum

a 8.20 kg particle P has a position vector of magnitude 6.90 m and angle θ1 = 42.0° and a velocity vector of magnitude 6.70 m/s and angle θ2 = 25.0°. Force , of magnitude 8.90 N and angle θ3 = 28.0° acts on P. All …
5. ### Physics

A particle with mass m = 1.20g and charge q = 345ìC is traveling in the x-direction with an initial velocity of v0 = 68.0m/s. The particle passes through a constant electric field in the y-direction with magnitude |E| = 263N/C over …
6. ### Physics

The three forces shown in the figure below act on a particle (with F1 = 50.0 N, F2 = 60.0 N, θ1 = 60.0°, and θ2 = 30.0°). If the particle is in translational equilibrium, find F3, the magnitude of force 3 and the angle …
7. ### physics

A PARTICLE OF MASS M IS SHOT WITH an initial velocity v making an angle b with the horizontal,the particle moves in the gravitational field of the earth. find the angular momentum of the particle about the origin when the particle …
8. ### particles of dynamics

A particle is released on the smooth inside wall of cylinder tank at A with velocity v0 which makes an angle β with horizontal tangent. The radius of the tank is r. Find the maximum height above point A reached by the particle, …
9. ### physics question

1-What is the shape of the trajectory of a charged particle moving in a uniform electric field if its initial velocity is null?
10. ### physics question help plz!

1-What is the shape of the trajectory of a charged particle moving in a uniform electric field if its initial velocity is null?

More Similar Questions