Review Questions: Newton's Laws of Motion
Answers
1. The tendency of objects to resist a change in motion is called:
a. Friction
b. Velocity
c. Inertia
d. Acceleration
e. Gravity
2. and it is measured by its
a. Speed
b. Velocity
c. Mass
d. ...all of these.
3. The force required to maintain a body at constant velocity in free space is equal to:
a. The mass of the body
b. Zero
c. The weight of the body
d. The force required to stop it
e. None of these.
Reasoning: For an object to move at constant velocity (meaning zero acceleration) the net force must be equal to zero.
4. This is in accordance with the law of:
a. Inertia
b. Action/reaction
c. Gravitation
d. Energy conservation.
5. In the absence of air resistance, a boulder and a pebble dropped from rest will fall with equal:
a. Momenta
b. Accelerations
c. Kinetic energies
d. ...all these.
6. The reason that this quantity is not greater for the heavier boulder than for the lighter pebble is that:
a. Both the boulder and the pebble fall at the same speed.
b. The initial potential energies of each is the same.
c. Gravitational force acting on each is the same.
d. The greater gravitational force on the boulder acts on a correspondingly greater mass.
Reasoning: see page 62, figure 4.10, in your textbook.
7. A heavy man and a light man parachute together from a high-flying plane. The first man to attain zero acceleration will be the:
a. Light man
b. Heavy man
c. Both will attain zero acceleration at the same time.
8. because:
a. The gravitational force on each man is the same.
b. Of the lesser gravitational force acting on the lighter man.
c. Air resistance will eventually counterbalance the weights of both men.
d. The lighter man will not have to fall for as long a time before the air resistance equals his weight.
9. In which case would you have the largest mass of gold? If you chunk of gold weighed 1 N on the:
a. Moon
b. Earth
c. Planet Jupiter
d. ....would be the same on each.
Reasoning: The gravitational acceleration on the moon is 1/6 of the earth. To have the same weight, we need more mass for the object on the moon.
10. This is because:
a. On the moon a greater mass of gold is required for the gravitational force to equal 1 N.
b. Weight and mass are directly proportional to each other.
c. Gravitational force per mass is greatest on the most massive planet.
11. A 100-N little physics type hangs on a rope suspended over a pulley as shown. The tension in the rope is:
a. 0 N
b. 50 N
c. 100 N
d. 200 N
12. It is interesting to note that:
a. The tension in the rope at this midpoint (uppermost part) is 100 N.
b. This is a modified tug o' war example (simply draped over a pulley).
c. The net force acting on the rope is in this case identical to the child's weight.
13. If an 800-N man hangs motionless from 4 vertical strangds of rope, then the tension in each strand of rope is:
a. 0 N
b. 200 N
c. 400 N
d. 800 N
14. which results in a net force on the man of
a. 0 N
b. 200 N
c. 400 N
d. 800 N
Reasoning:Since the man is motionless, the net force on him must be zero.
15. Neglecting air resistance, friction, and rotational inertia of the wheels, if two identical cars, one empty and the other with four heavy passengers, start rolling down a hill together, the heavier car will get to the bottom:
a. Before the empty car,
b. After the empty car,
c. At the same time as the empty car.
16. while in the presence of air resistance, the heavier car will get to the bottom:
a. Before the empty car.
b. After the empty car.
c. At the same time as the empty car.
Reasoning:When there is air resistance, the motion of the heavier car will be less retarded. It will reach the bottom before the lighter car.
17. A 100-newton sack of potatoes falls from an airplane. As the velocity of fall increases, the air resistance acting on the falling sack also increases. When air resistance equals 100 N, the acceleration of the sack will be:
a. Zero
b. 4.9 m/s2
c. 9.8 m/s2
d. 100 m/s2
18. and the velocity of the sack will be:
a. 0 m/s
b. 4.9 m/s
c. 9.8 m/s
d. 100 m/s
e. Constant.
19. In referring to how much matter a body contains, we use the term:
a. Volume
b. Mass
c. Weight
20. and the force of gravitational attraction upon a body is:
a. Weight
b. Volume
c. Mass.
21. An elephant and a feather fall through the air. The force of air resistance is greatest on the:
a. Feather
b. Elephant
c. ...the same on each
22. because:
a. The feather weighs less.
b. The elephant encounters more air because of his greater size.
c. Each is under the influence of gravitational force alone.
23. If an object has twice as much mass as another, then it also has twice as much:
a. Acceleration
b. Weight
c. Center of gravity
d. Area
24. this is because:
a. Of inertia
b. Mass and weight are directly proportional to each other
c. The gravitational force acting on all objects in the same locality is the same.
25. If a body is moving at constant velocity along a straight line, it must have:
a. A constant net force acting upon it
b. Constant non-zero acceleration
c. Constant speed
d. None of the above.