# AP Physics

posted by .

At time t=0, a 2kg particle has position vector r=(5.0m)i+(-8.0m)j relative to the origin. Its velocity just then is given by v=(-5.0t^2m/s)i. For the following answers, use t for the time. A) About the origin and for t>0, what is the particle's angular momentum? B) About the origin and for t>0, what is the torque acting on the particle? C) Repeat A and B for a point with coordinates (-7.0m, -4.0m, 0.0m) instead of the origin.

• AP Physics -

Please don't post under different names.

I will be happy to critique your thinking on this.

• AP Physics -

L = R x m V
where R is position vector from reference point origin for a and b) to mass
V is velocity vector
x means cross or vector product

the x coordinate of the position vector is 5 at the start but changes with time because the thing has x velocity of -5t^2
integral = 5-(5/3) t^3

so for part a
L = (5-5t^3/3) i - 8 j)x(-5 t^2 i + 0 j)

(5-5t^3/3) -8 0
-5t^2 0 0 = -40 t^2 k
i j k

for part b
Torque = rate of change of angular momentum
dL/dt = d/dt(40 t^2 k) = 80 t

for part c
Rx = 5-5t^3/3 - (-7) = 12 - 5 t^3/3
Ry = -8 -(-4) = -4
Rz = 0 still
just do it again

• determinant sign error -

(5-5t^3/3) -8 0
-5t^2 0 0 = +40 t^2 k
i j k

## Similar Questions

1. ### Physics

A particle initially located at the origin has an acceleration of a= 5.00J^ m/s^2 and an initial velocity of v0= 8.00I^ m/s A) Find the vector position at any time t where t is measured in seconds. Find the vector velocity at any time …
2. ### Physics

A particle is in uniform circular motion about the origin of an xy coordinate system, moving clockwise with a period of 3.50 s. At one instant, its position vector (from the origin) is r = (8.00 m) ihat - (7.00 m) jhat. At that instant, …
3. ### physics

A particle leaves the origin with an initial velocity = (2.35 m/s) and moves with constant acceleration = (-1.90 m/s2) + (2.60 m/s2)>. (a) How far does the particle move in the x direction before turning around?
4. ### physics

The acceleration of a particle moving only on a horizontal plane is given by a= 3ti +4tj, where a is in meters per second-squared and t is in seconds. At t = 0s, the position vector r= (20.0 m)i + (40.0 m)j locates the particle, which …
5. ### physics

The acceleration of a particle moving only on a horizontal plane is given by a= 3ti +4tj, where a is in meters per second-squared and t is in seconds. At t = 0s, the position vector r= (20.0 m)i + (40.0 m)j locates the particle, which …
6. ### Calc3

A particle initially at the origin travels in uniform motion with velocity v=2i-j-2k. Find position venctor vector r(t) of a particle at time t. Find equatio for the plane passing through the origin and perp. to the tragectory of the …
7. ### mechanics and heat

The position vector of a particle of mass m = 2kg in the xy plane is given: r = (t-2)i + (2t +1)j (meter) where t is in seconds . Find the torque exerted on the particle about the origin.
8. ### Physics

In the time interval from 0.0 s to 10.1 s, the acceleration of a particle traveling in a straight line is given by ax = (0.1 m/s3)t. Let to the right be the +x direction. The particle initially has a velocity to the right of 10.0 m/s …
9. ### Physics

The velocity graph of a particle moving along the x-axis is shown. The particle has zero velocity at t=0.00s and reaches a maximum velocity, vmax, after a total elapsed time, t total. If the initial position of the particle is x0 =6.22m, …
10. ### physics

A 2.51 kg particle moves in the xy plane with a velocity of v = ( 4.98 , -3.58 ) m/s. Determine the angular momentum of the particle about the origin when its position vector is r = ( 1.73 , 1.15 ) m.

More Similar Questions