Topic: Angular Momentum

I have no clue how to figure these out. Please help me.

1)What is the angular momentum for a 2kg ball being swung in a circle of radius 3m at a speed of 4 m/s?

2)A 3 kg object is moving in a circle with a speed of 5 m/s. If the angular momentum of the object is 30 kgm2/s, what is the radius of the circle?

3)A solid disk is rotating at an angular speed of 3 rad/s. If the mass of the disk is 10 kg and a radius of 2m, what is the angular momentum of the disk?

4)A thin ring of mass 3kg and radius 1 m has a momentum of 90 kgm2/s. What is the angular velocity of the ring?

1. The angular momentum of the ball  is

24kg.m2/s

2. The radius of the circle is 2 m

3. The angular momentum of the disk is 

60kg.m2/s

4. The angular velocity of the ring is 30 rad/s

Step-by-step explanation

1. The mass of ball (M)=2kg

The radius of a circle (R)=3m

The speed (v)=4m/s

The angular momentum of the ball (L) is

L=MvR

L=(2)(4)(3)

L=24kg.m2/s

2. The mass of object (M)=3kg

The speed (v)=5m/s

The angular momentum of the object (L)=30kg.m2/s

The radius of the circle (R) is

L=MvR

R=MvL?

R=(3)(5)30?

R=2m

3. The angular speed (ω)=3rad/s

The mass of disk (M)=10kg

The radius (R)=2m

The moment inertia of disk (I)=½MR2

The angular momentum of the disk (L) is

L=Iω

L=½MR2ω

L=½(10)(2)2(3)

L=60kg.m2/s

4. The mass of ring (M)=3kg

The radius (R)=1m

The angular momentum (p)=90kg.m2/s

The inertia moment of thin ring (I)=MR2

The angular velocity of the ring (ω) is

L=Iω

L=MR2ω

ω=MR2L?

ω=(3)(1)290?

ω=30rad/s