50. A sled is on an icy (frictionless) slope that is 30
◦
above the horizontal. When a 40-N force,
parallel to the incline and directed up the incline, is applied to the sled, the acceleration of the
sled is 2.0m/s
2
, down the incline. The mass of the sled is:
A. 3.8kg
B. 4.1kg
C. 5.8kg
D. 6.2kg
E. 10 kg
ans: E
51. When a 40-N force, parallel to the incline and directed up the incline, is applied to a crate on
a frictionless incline that is 30
◦
above the horizontal, the acceleration of the crate is 2.0m/s
2
,
up the incline. The mass of the crate is:
A. 3.8kg
B. 4.1kg
C. 5.8kg
D. 6.2kg
E. 10 kg
ans: C
52. The “reaction” force does not cancel the “action” force because:
A. the action force is greater than the reaction force
B. they are on different bodies
C. they are in the same direction
D. the reaction force exists only after the action force is removed
E. the reaction force is greater than the action force
ans: B
53. A book rests on a table, exerting a downward force on the table. The reaction to this force is:
A. the force of Earth on the book
B. the force of the table on the book
C. the force of Earth on the table
D. the force of the book on Earth
E. the inertia of the book
ans: B
54. A lead block is suspended from your hand by a string. The reaction to the force of gravity on
the block is the force exerted by:
A. the string on the block
B. the block on the string
C. the string on the hand
D. the hand on the string
E. the block on Earth
ans: E
60 Chapter 5: FORCE AND MOTION – I