**Chapter 12 Practice 3**

Torque and Dynamics

Torque and Dynamics

As an example here is a beam with two

masses on the ends.

A

B

C

D

Which of these forces

will produce the most

Torque

A

B

C

D

Which of these forces

will produce a positive

value of torque?

A A & B

B C & D

C B

D A

An object's moment of inertia is 2.0 kg m^2. Its angular velocity is increasing at a rate of 4.0 rad/s per second. What is the torque on the object?

8 Nm

Blocks of mass m1 and m2 are connected by a massless string that passes over a pulley. The pulley turns on frictionless bearings. Mass m1 slides on a horizontal, frictionless surface. Mass m2 is released while the blocks are at rest.

A. Assume the pulley is massless. Find the acceleration of m1 and the tension in the string

B. Suppose the pulley has a mass of mp and a radius of R. Find the acceleration of m1 and the tensions in both parts of the string.

m 1

m 2

The 2.0 kg, 30 cm diameter disk is spinning at 300 rpm. how much friction force must the brake apply to the rim to bring the disk to a halt in 3.0 s?

**4.7 N**

The 28-cm-diameter disk here, can rotate on an axle through its center. What is the net torque about the center?

-2.1 N m

The axle in (Figure 1) is half the distance from the center to the rim. Suppose d = 35 cm. What is the magnitude of the torque that the axle must apply to prevent the disk from rotating?

17 N

A 4.0 kg, 36-cm-diameter metal disk, initially at rest, can rotate on an axle along its axis. A steady 8 N tangential force is applied to the edge of the disk. What is the disk's angular velocity, in rpm, 4.0 s later?

850 rpm

The sphere of mass M and radius R is rigidly attached to a thin rod of radius r that passes through the sphere at distance 1/2R from the center. A string wrapped around the rod pulls with tension T. Find an expression for the sphere's angular acceleration. The rod's moment of inertia is negligible.

Can you help explain Torque please?

How does torque relate to force?

Why is it that with gravitational torque, it's treated as if all the mass were in it's center of mass instead of where the axle is?

could you explain how newtons second law applies to this?

The marble rolls down the track and around a loop-the-loop of radius R. The marble has mass m and radius r.