In these figures, we see a boy named Billy riding a carnival ride called the Rotor and the free-body diagram for the forces acting on him. What must be the magnitudes of the vectors fwall,Billy and WEarth,Billy if Billy remains at the same height along the wall?
a. fwall,Billy is greater than WEarth, Billy to keep Billy from falling.
b. The magnitudes of fwall,Billy and WEarth, Billy are equal.
c. fwall,Billy depends on the magnitude of Nwall,Billy, but the magnitude of WEarth,Billy is always the same.
d. Nwall,Billy and fwall,Billy must be equal in magnitude.
[Ques. 2] Why is acceleration a vector?
a. Because it can only describe a slowing down or speeding up.
b. Because it is a measurement of change.
c. Because acceleration is the rate of change of velocity, which is itself a vector.
d. Because it is measured in (meters per second) per second.
e. Because it relates to speed.
[Ques. 3] To subtract a vector from another vector:
a. add the two vectors and make the result negative.
b. draw an arrow from the tail of the first vector to the head of the second.
c. draw an arrow from the head of the first vector to the tail of the second.
d. turn the arrow you are subtracting around, and then add.
e. put one on top of the other, put a minus sign by the lower one, and then subtract as if they were numbers.
[Ques. 4] When an object is moving in a circle, but it is not held to the center by a tangible connection like a string, what provides the centripetal force?
a. The tendency for the object to move in a straight line.
b. The natural tendency to move in a circle.
c. The angle of the surface the object moves on.
d. Centrifugal force.
e. Some force such as friction or gravity.
[Ques. 5] If you are whirling a ball on a string and you suddenly cut the string, what happens?
a. The ball falls immediately to the ground.
b. The ball keeps traveling in the same circle.
c. The ball goes off in some random straight line.
d. The ball goes off in a straight line based on where it was heading when the string was cut.
e. The ball goes off in a straight line path directed radially outward from the center of the circle.
[Ques. 6] What is centripetal force?
a. A force that seeks the center of a circle.
b. A force that seeks the edge of a circle.
c. A force that makes an object stop traveling in a circle.
d. A force that turns the pedals of a bicycle.
e. A force that keeps an object from hitting the ground.
[Ques. 7] The change in velocity vector shown in the figure points in what direction? (Hint: see Figure 4-5.)
a. Tangent to the circle.
b. Pointing to the center of the circle.
c. Pointing away from the center of the circle.
d. Pointing perpendicular to the circle.
e. Always to the left.
[Ques. 8] A girl whirls a ball on the end of a string above her head. Assume the motion of her hand to keep the ball in motion is negligible. For the ball to remain in a circular path while it rotates with a constant speed:
a. only the centripetal force shown in the figure is required.
b. in addition to the centripetal force shown in the figure, there must also be a force tangent to the motion of the ball.
c. in addition to the centripetal force shown in the figure, there must also be a centrifugal force that pulls the ball outward.
d. in addition to the centripetal force shown in the figure, there must also be a force radially inward from the string to cause circular motion.
e. the centripetal force inward and the centrifugal force outward must balance each other.
[Ques. 9] Which of these undergoes circular motion?
a. A bullet shot from a gun.
b. A top spinning on a table.
c. A baseball hit by a bat.
d. A satellite orbiting the Earth.
e. An apple falling out of a tree.
[Ques. 10] Why does a parachutist stop accelerating downward after opening the chute and then falling some distance?
a. Because of the influence of the parachute, there is no longer a pull on the parachutist due to gravity.
b. The parachutist's weight becomes zero as a result of the tug of the parachute.
c. Air resistance produces a pull on the parachutist that is equal and opposite to the pull of gravity.
d. The speed of freely falling objects is a constant.
e. All objects fall with the same acceleration.
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