physics ch 9

A horizontal disk rotates about a vertical axis through its center. Point P is midway between the center and the rim of the disk, and point Q is on the rim. If the disk turns with constant angular velocity, which of the following statements about it are true? (There may be more than one correct choice.) a))) Q is moving twice as fast as P. b))) The linear acceleration of Q is twice as great as the linear acceleration of P. c))) P and Q have the same linear acceleration. d))) The angular velocity of Q is twice as great as the angular velocity of P. e))) The linear acceleration of P is twice as great as the linear acceleration of Q.

a, b

A dumbbell-shaped object is composed by two equal masses, m, connected by a rod of negligible mass and length r. If I1 is the moment of inertia of this object with respect to an axis passing through the center of the rod and perpendicular to it and I2 is the moment of inertia with respect to an axis passing through one of the masses, it follows that... a))) I 1 > I 2. b))) I 2 > I 1. c))) I 1 = I 2. I1=2m[r/2]^2 =1/2mr^2 I2=mr^2 therefore I2>I1

b

As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it? a))) to your right b))) to your left c))) down d))) forwards e))) up

c

When a rigid body rotates about a fixed axis, all the points in the body have the same... a))) tangential acceleration. b))) linear displacement. c))) centripetal acceleration. d))) angular acceleration. e))) tangential speed.because all formulas come from when angular acceleration is constant

c

When you ride a bicycle, in what direction is the angular velocity of the wheels? a))) to your right b))) forwards c))) to your left d))) backwards e))) upViewed from the left, the rotation is CCW, so, using the right hand rule, the angular velocity vector (and therefore also the angular momentum vector) is towards the viewer, which is to the left of the rider.

c