# PSC 2121 Lecture Notes - Lecture 5: Mechanical Equilibrium, Net Force

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Physical Science PSC2121

Review Final Exam

Fall 2015

Chapters 1-4

1. Place a book that weighs 10 N on a horizontal surface and the support force on the book

is

A) less than 10 N.

B) 10 N.

C) greater than 10 N.

D) dependent on whether the book lies flat or stands upright.

2. When you stand at rest on a pair of bathroom scales, the readings on the scales will

always

A) each be half your weight.

B) each equal your weight.

C) add to equal your weight.

D) add up to more than your weight.

3. If a non-rotating object has no acceleration, then we can say for certain that it is

A) at rest.

B) moving at constant nonzero velocity.

C) in mechanical equilibrium.

D) all of the above

E) none of the above

4. The force of friction on a sliding object is 10 N. The applied force needed to maintain a

constant velocity is

A) more than 10 N.

B) less than 10 N.

C) 10 N.

5. When you push your desk to the right, friction on the desk acts toward

A) the left.

B) the right.

C) at right angles to your push.

D) none of the above

6. The resistive force of friction occurs for

A) solids.

B) liquids.

C) gases.

D) all of the above

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Physical Science PSC2121

7. At the end of two seconds of free fall, an object released from rest will have a speed of

A) 5 m/s.

B) 10 m/s.

C) 15 m/s.

D) none of the above

8. One-half second after starting from rest, a freely falling object will have a speed of about

A) 5 m/s.

B) 10 m/s.

C) 15 m/s.

D) none of the above

9. If you toss a ball straight upward at 40 m/s with no air resistance, 6 seconds later its

speed is

A) zero.

B) 10 m/s.

C) 20 m/s.

D) 30 m/s

E) 40 m/s.

10. Inside the interior of a truck that moves at constant velocity is a package that drops from

the midpoint of the ceiling. The package hits the floor

A) exactly below the midpoint of the ceiling.

B) ahead of the midpoint of the ceiling.

C) behind the midpoint of the ceiling.

D) more information is needed

E) none of the above

11. If the mass of an object does not change, a constant net force on the object produces

constant

A) velocity.

B) acceleration.

C) both

D) none of the above

12. A 10-N block and a 1-N block lie on a horizontal frictionless table. To push them with

equal acceleration, we would have to push with

A) equal forces on each block.

B) 10 times as much force on the heavier block.

C) 10 squared or 100 times as much force on the heavier block.

D) one-tenth as much force on the heavier block.

E) none of the above

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