1) A circular saw spins at 4000 rev/s and its brake stops it in exactly 3s. Assu

Question

1) A circular saw spins at 4000 rev/s and its brake stops it in exactly 3s. Assuming constant angular acceleration, how many revs does the blade make while the brake is applied?

A) 2700, B) 3000, C) 6000

2)Consider a piece of clay stuck near the edge of a potters wheel. When the potters wheel is moving with a constant, non-zero angular speed, which statement is flase?

A) The piece of clay is moving with a constant speed.

B) The piece of clay has zero acceleration

C) The piece of clay has zero tangential acceleration

3)A constant, non-zero net torque is exerted on an object, Which of the following quantities must necessarily change with time?

A) Angular position, angular velocity, angular acceleration

B) Angular position, angular acceleration, Kinetic energy

C) Angular positionm angular velocity, Kinetic energy

4) A ball of mass m with initial speed v collides with another ball of mass M that is initially at rest. If the two balls stick together and have a final speed of V, whats is the ratio of v/V?

A) (M+m)/m

B) (M+m)/M

C) (2M)/(M+m)

D) (M^2)/(M+m)

5)Andy and charlie are riding a merry-go-round. Andy rides at a point on the outer rim of the circular platform, three times farther from the center of the platform than charlie is riding. When the merry-go-round is rotating at constant angular speed w, which one of the following statements is correct?

A) Andy has zero angular acceleration.

B) The angular speed of Andy is three times that of Charlie.

C) The angular acceleration of Andy nine times that of Charlie.

6) In a min-air collision between a ping pong ball and a baseball, which experiences the larger change in momentum?

A) Each will experience an equal (and opposite) change in momentum.

B) The baseball will have a larger chaneg in momentum.

C) Which ever had a larger initial velocity will ahve a larger change in momentum.

Explanation / Answer

1) w = 4000 rev/s , t = 3s

from rotational kinematic equations

w =w0 +at

a = 4000/3 rev/s^2

theta = wot +(1/2)at^2

= 0 +(0.5*4000*3*3/3)^2 =6000 rev

correct option is (C)

2) Correct option is (B)

3) correct option is (C)

4) from conservation of momentum

mv +0 = (m+M)V

v/V = m+M/m

correct option is (A)

5) rA = 3rC, wA = wC

v = rw

vA/vC = rA/rC = 3

correct option is (B)

6) correct option is (A)

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