Back Questions on Circular Motion
1.
Which of the following is an example of an "inertial force"?
a)
b)
c)
d)
2.
I slam on the brakes of my moving car; the car stops.
I slam on the brakes of my moving car; the pizza on the seat beside me slides off the seat.
Any existing centripetal force.
Any effect for which Newton's third law holds.
Which of the following is an example of an inertial force?
a) The Coriolis force.
b) Buoyancy
3.
So-called "inertial forces" are a result of
a)
b)
c)
d)
4.
the sum of all of the forces keeping an object in a circle.
the sum of all of the forces tending to make an object move to the outside of a circle.
an inertial force postulated to satisfy Newton's laws in a rotating reference frame.
all of the above.
The Coriolis force, or Coriolis effect,
a)
b)
c)
d)
e)
6.
the application of Newton's third law in a non-reciprocal reference frame.
the application of Newton's third law in a reciprocal reference frame.
attempting to apply Newton's laws in an inertial frame of reference.
attempting to apply Newton's laws in a non-inertial frame of reference.
The centrifugal effect is
a)
b)
c)
d)
5.
c) The centripetal force on an object moving in a circle.
d) The terminal velocity reached by a skydiver.
pushes stationary objects to the right in the Northern Hemisphere.
pushes moving objects to the right in the Northern Hemisphere.
pushes stationary objects to the left in the Northern Hemisphere.
both (a) and (b).
both (b) and (c).
In the Southern Hemisphere, the Coriolis force will push moving objects
a) from right to left.
b) from left to right.
c) from East to West.
d) from West to East.
7.
Centripetal force is
a)
b)
c)
d)
8.
only to be identified with the one force that keeps an object moving in a circle.
the sum of all of the forces on an object moving in a circle.
equal and opposite to the centrifugal force, in the sense of Newton’s second law.
equal and opposite to the centrifugal force, in the sense of Newton’s third law.
The sum of the forces on an object moving at constant speed in a circle is equal to
a) (mv2)/r, inward.
b) ma, where a is the vector acceleration.
c) the centripetal force.
9.
If I am in outer space, and I am using a rope to twirl an object that weighs 39.2 N on earth in
a circle of radius 4 meters at a speed of 10 m/s, then the tension in the rope is
a) 25 N.
b) 980 N.
10.
c) 100 N
d) 24.5 N
I whirl a ball around me (in outer space) in a horizontal circle by holding onto a string attached
to the ball. The rope, therefore, provides the centripetal force (call it T, for tension) for the
ball. The equal and opposite force to T (in the sense of Newton's third law) is
a) the centrifugal force on the ball.
b) the force of the ball on my hand.
11.
c) the force of the ball on the rope.
d) unable to be determined.
Assume that a car is moving a constant speed of 50 mph along a straightaway. It enters a
curve, and maintains a speed of 50 mph while it goes around the curve. The force of the road
on the car is __________ while the car is in the curve than while the car is in the straight
away. Include the effects of air resistance.
a) smaller
12.
d) (a) and (c) but not (b).
e) (a) and (b) and (c).
b) the same as
c) larger
Assume that I am on a ferris wheel rotating so that the seats move with a constant speed v.
Where is my apparent weight the smallest?
a) At the top.
d) Can't say: the answer depends on the speed v.
b) At the bottom.
e) Can't say; the answer depends on my mass.
c) When my seat is halfway between top and bottom.
13.
If you are moving in a vertical circle at constant speed, like on a Ferris wheel, your apparent
weight is greatest at the
a) center.
b) top.
14.
It is possible for an object to be apparently weightless when moving in a vertical circle.
a) True.
15.
b) False.
c) There is not enough information.
is greatest when the rock is at the bottom of its trajectory.
is greatest when the rock is at the top of iis trajectory.
is constant independent of the position of the rock.
there is not enough information to make any of the above statements
Assume that I am on a Ferris wheel that is rotating. We know that my apparent weight will be
smallest at the top of the wheel. For which of the following Ferris wheel speeds will that
apparent weight be the smallest?
a) 15 m/s
b) 30 m/s
18.
c) There is not enough information.
I tie a rock to a string, and use the string to spin the rock in a vertical circle at constant speed.
The tension in the string
a)
b)
c)
d)
17.
b) False.
It is possible for an object to be apparently weightless when moving in a horizontal circle.
a) True.
16.
c) side.
d) bottom.
c) Can’t tell unless I give you my mass.
d) Can’t tell unless I give you the radius of the wheel.
Consider a person in an airplane at the top of a looping, circular trajectory, like the
"Vomit Comet" that we discussed in class. At this point, the person's
a) apparent weight is equal to his or her true weight.
b) apparent weight can be zero.
19.
c) true weight is zero.
d) none of the above.
Which of the following, (a) or (b), if either, is larger? (Careful!! if we haven’t done gravity
yet, don’t worry about this one.)
a)
b)
c)
d)
The measured acceleration due to gravity, g, at the equator.
The measured acceleration due to gravity, g, at the North pole.
Neither; the measured values of g are the same at the equator and the North pole.
There is not enough information.
20.
On a flat curve, the force(s) that provide(s) the centripetal force for a turning car is (are)
a)
b)
c)
d)
21.
On a banked curve, the force(s) that provide(s) the centripetal force for a turning car is (are)
a)
b)
c)
d)
22.
the friction between the car and the road.
the friction between the car and the road and the support force of the road on the car.
the gravitational force on the car.
none of the above.
the friction between the car and the road.
the friction between the car and the road and the support force of the road on the car.
the gravitational force on the car.
none of the above.
A banked curve is safer than a flat curve because
a)
b)
c)
d)
it eliminates the need for a centripetal force.
it increase the friction between the road and the car.
the support force contributes to the centripetal force.
the speed limits are larger on banked curves than flat curves.
Answer Key:
1. B
2. A
3. D
4. C
5. B
6. A
7. B
8. E
9. C
10. C
11. C
12. A
13. D
14. A
15. B
16. A
17. B
18. B
19. B
20. A
21. B
22. C