PHYSICS : SHEET LAWS OF MOTION
LAWS OF MOTION PASSAGE TYPE QUESTIONS
PASSAGE # 1 A moving company uses the pulley system in figure 1 to lift heavy crates up a ramp. The ramp is coated with rollers that make the crate’s motion essentially frictionless. A worker piles cinder blocks onto the plate until the plate moves down, pulling the crate up the ramp. Each cinder block has mass 10 kg. The plate has mass 5 kg. The rope is nearly massless, and the pulley is essentially frictionless. The ramp makes a 30° angle with the ground. the crate has mass 100 kg.
Cr ate
30°
Plate
Let W1 denote the combined weight of the plate and the cinder blocks piled on the plate. Let T denote the tension in the rope. And let W2 denote the crate’s weight. 1.
What is the smallest number of cinder blocks that need to be placed on the plate in order to lift the crate up the ramp? (A) 3 (B) 5 (C) 7 (D) 10
2.
Ten cinder blocks are placed on the plate. As a result, the crate accelerates up the ramp. W hich of the following is true?
3.
(A) W1 T W2 sin 30
(B) W1 T W2 sin 30
(C) W1 T W2 sin 30
(D) W1 T W2 sin 30
The ramp exerts a “normal” force on the crate, directed perpendicular to the ramp’s surface. This normal force has magnitude: (B) W2 sin 30
(A) W2 4.
(D) W2 sin 30 cos 30
(C) T W2 sin 30
(D) T W2
The net force on the crate has magnitude: (A) W1 W2 sin 30
5.
(C) W2 cos 30
(B) W1 W2
After the crate is already moving, the cinder blocks suddenly fall off the plate. Which of the following graphs best shows the subsequent velocity of the crate, after the cinder blocks have fallen off the plate? (Up theramp is the positive direction.)
+ v 0
(A) A
A time
+ v 0
B time
(B) B
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+ v 0
(C) C
C
+ v time
0
D
time
(D) D
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