1861 words - 8 pages

1) Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P. The tension in the wire is T (see figure). Which one of the following relationships between T and P must be true?

A) T > P

B) T = P

C) P + T = 125 N

D) P = T + 25 N

E) P = T + 100 N

2) Two objects having masses m1 and m2 are connected to each other as shown in the figure and are released from rest. There is no friction on the table surface or in the pulley. The masses of the pulley and the string connecting the objects are completely negligible. What must be true about the tension T in the string just after the objects are released?

A) T = m2g

B) T > m2g

C) T < m2g

D) T = m1g

E) T > m1g

3) A brick is resting on a rough incline as shown in the figure. The friction force acting on the brick, along the incline, is

A) zero.

B) equal to the weight of the brick.

C) greater than the weight of the brick.

D) less than the weight of the brick.

4) If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out because an outward force balances the pull of gravity on the water.

A) True

B) False

5) Suppose a highway curve is properly banked to eliminate friction for a speed of 45 mph. If your tires were bald and you wanted to avoid sliding on the road, you would have to drive

A) somewhat below 45 mph.

B) somewhat above 45 mph.

C) at exactly 45 mph.

6) Suppose the force of the air drag on an object is proportional to the speed of the object and in the direction opposite the object's velocity. If you throw an object upward, the magnitude of its acceleration is greatest

A) right after the object is released.

B) at the top of its trajectory.

C) The acceleration of the object is the same throughout the entire trajectory.

7) A 60.0-kg person rides in elevator while standing on a scale. The elevator is traveling downward but slowing down at a rate of 2.00 m/s2. The reading on the scale is closest to

A) 589 N.

B) 708 N.

C) 469 N.

D) 120 N.

E) 349 N.

8) Two objects are connected by a very light flexible string as shown in the figure, where and . You can ignore friction and the mass of the pulley.

(a)

Draw free-body diagrams for each object.

(b)

Calculate the magnitude of the acceleration of each object. 4.38 m/s^2

(c)

Calculate the tension in the string. 17.74N

9) Three boxes in contact rest side-by-side on a smooth, horizontal floor. Their masses are 5.0-kg, 3.0-kg, and 2.0-kg, with the 3.0-kg box in the center. A force of 50 N pushes on the 5.0-kg box, which pushes against the other two boxes.

(a)

Draw the free-body diagrams for each of the boxes.

(b)

What magnitude force does the 3.0-kg box exert on the 5.0-kg box?25 N

(c)

What magnitude force does the 3.0-kg box exert on the 2.0-kg box?10 N

10) The figure shows a 100-kg block being released from rest from a height of 1.0 m. It then takes it 0.90 s to reach the floor. What is the mass m of the other block? The pulley has no appreciable mass...

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