Physics 8

A circular hoop rolls without slipping on a flat horizontal surface. Which one of the following is necessarily true? a) All points on the rim of the hoop have the same speed. b) All points on the rim of the hoop have the same velocity. c) Every point on the rim of the wheel has a different velocity. d) All points on the rim of the hoop have acceleration vectors that are tangent to the hoop. e) All points on the rim of the hoop have acceleration vectors that point toward the center of the hoop.

c) Every point on the rim of the wheel has a different velocity.

A long thin rod of length 2L rotates with a constant angular acceleration of 10 rad/s^2 about an axis that is perpendicular to the rod and passes through its center. What is the ratio of the tangential speed (at any instant) of a point on the end of the road to that of a point distance L/2 form the end of the rod? A) 1:1 B) 1:2 C) 2:1 D) 4:1 E) 1:4

C) 2:1

A 2.0-kg solid disk rolls without slipping on a horizontal surface so that its center proceeds to the right with speed 5.0 m/s. The point A is the uppermost point on the disk and the point B is along the horizontal line that connects the center of the disk to the rim. If the disk now speeds up, what is the direction of the disk's angular acceleration? A) to the left B) to the right C) into the paper D) out of the paper E) it varies form point to point on the disk

C) into the paper

A wheel, originally rotating CCW at 126 rad/s undergoes a constant angular deceleration of 5.00 rad/s^2. what is its angular velocity after it has turned through an angle of 628 radians? A)+15 rad/s B)-15 rad/s C)+98 rad/s D)-98 rad/s E)+150 rad/s F)-150 rad/s

C)+98 rad/s

A fan rotating CW with an initial angular velocity of 1000 rev/min is switched off. In 2 seconds, the angular velocity decreases to 200 rev/min. Assuming the angular acceleration is constant, what is the blade's displacement during this time? A) +20 rad B) -20 rad C) +126 rad D) -126 rad E) +1260 rad F) -1260 rad

D) -126 rad

A car is moving along a horizontal road at a constant velocity that is directed at 45 degrees south of east. What is the direction of the angular velocity of the wheels of the car? A) 45 south of west B) 45 north of west C) 45 south of east D) 45 north of east E) due east

D) 45 north of east

On an amusement park ride, passengers are seated in a horizontal circle of radius 7.5 m. The seats begin form rest and are uniformly accelerated for 21 seconds to a maximum rotational speed of 1.4 rad/s. What is the tangential speed of the passengers after 15 s after the acceleration begins? A) .067 m/s B) .50 m/s C) 1.4 m/s D) 7.5 m/s E) 11 m/s

D) 7.5 m/s

A grindstone of radius 4.0 m is initially spinning with an angular speed of 8.0 rad/s. The angular speed is then increased to 10 rad/s over the next 4.0 seconds. Assume that the angular acceleration is constant. Through how many revolutions does the grindstone turn during the 4.0 second interval? A) .64 B) 3.8 C) 4.0 D) 5.7 E) 36

5.7

On an amusement park ride, passengers are seated in a horizontal circle of radius 7.5 m. The seats begin form rest and are uniformly accelerated for 21 seconds to a maximum rotational speed of 1.4 rad/s. Assume a CCW rotation. What is the tangential acceleration of the passengers during the first 21 s father ride) A) .067 m/s^2 B) .50 m/s^2 C) 1.4 m/s^2 D) 7.5 m/s^2 E) 11 m/s^2

B) .50 m/s^2

A circular disk of radius 2.0 m rotates, starting from rest, with a constant angular acceleration of 20.0 rad/s^2. What is the centripetal acceleration of a point on the edge of the disk at the instant that its angular speed is 1.0 rev/s? A) 40 m/s^2 B) 79 m/s^2 C) 110 m/s^2 D) 120 m/s^2 E) Zero

B) 79 m/s^2