An airplane flies in a horizontal circle of radius 500 m at a speed of 150 m/s. If the plane were to fly in the same 500-m circle at a speed of 300 m/s, by what factor would its centripetal acceleration change?
a. 0.25
b. 0.50
c. 1.00
d. 2.00
e. 4.00
[Ques. 2] A skydiver of 75-kg mass has a terminal velocity of 60 m/s. At what speed is the resistive force on the skydiver half that when at terminal speed?
a. 15 m/s
b. 49 m/s
c. 30 m/s
d. 42 m/s
e. 36 m/s
[Ques. 3] A boy on board a cruise ship drops a 30.0 g marble into the ocean. If the resistive force proportionality constant is 0.500 kg/s, what is the terminal speed of the marble in m/s?
a. 0.147
b. 0.294
c. 0.588
d. 1.18
e. 2.35
[Ques. 4] Frank says that if you release the string when swinging a ball in a horizontal circle, the ball flies out in the radial direction defined by the string at the instant you release the ball. John says that it flies out along a tangent line perpendicular to the string, and that it then drops straight down to the ground. Which one, if either, is correct?
a. Frank, because the centrifugal force is no longer counteracted by the string.
b. Frank, because balls naturally fly straight out.
c. John, because there is no centrifugal force.
d. John, because balls fall straight down when released.
e. Neither, because although there is no centrifugal force, and the ball's velocity is tangent to the circle at the instant of release, the ball then follows a parabolic trajectory.
[Ques. 5] A hornet circles around a pop can at increasing speed while flying in a path with a 12-cm diameter. We can conclude that the hornet's wings must push on the air with force components that are
a. straight down.
b. down and inwards.
c. down and outwards.
d. down and backwards.
e. down, backwards and outwards.
[Ques. 6] A hornet circles around a pop can at constant speed once per second in a path with a 12-cm diameter. We can conclude that the hornet's wings must push on the air with force components that are
a. straight down.
b. down and inwards.
c. down and outwards.
d. down and backwards.
e. down, inwards and backwards.
[Ques. 7] Two small cylindrical plastic containers with flat bottoms are placed on a turntable that has a smooth flat surface. Canister A is empty; canister B contains lead shot. Each canister is the same distance r from the center. The coefficient of static friction between the canisters and the turntable is s. When the speed of the turntable is gradually increased,
a. only the lighter container slides outward off the turntable; the heavier one stays on.
b. only the heavier container slides outward off the turntable; the lighter one stays on.
c. both containers slide off the turntable at the same turntable speed.
d. the lighter container slides inward.
e. the heavier container slides inward.
[Ques. 8] An iceboat is traveling in a circle on the ice. Halfway around the circle the sail and the steering mechanism fall off the boat. Which statement is correct?
a. The boat will continue traveling in the circle because there is no friction.
b. The boat will continue to travel in the circle because its velocity exerts a force on it.
c. The boat will move off on a line tangent to the circle because there is no force on it.
d. The boat will move off tangent to the circle because there is a force on it perpendicular to the boat directed to the outside of the circle.
e. The boat will move off to the outside perpendicular to the tangent line since a force directed to the outside of the circle always acts on the boat.
[Ques. 9] When a car goes around a circular curve on a level road without slipping,
a. no frictional force is needed because the car simply follows the road.
b. the frictional force of the road on the car increases when the car's speed decreases.
c. the frictional force of the road on the car increases when the car's speed increases.
d. the frictional force of the road on the car increases when the car moves to the outside of the curve.
e. there is no net frictional force because the road and the car exert equal and opposite forces on each other.
[Ques. 10] For a plane to be able to fly clockwise in a horizontal circle as seen from above, in addition to exerting a force downwards on the air
a. it must be increasing its speed.
b. it must exert a force on the air that is directed to the plane's left side.
c. it must exert a force on the air that is directed to the plane's right side.
d. it does not need to exert a force: it must only move the wing flaps out.
e. it only needs to deflect the air without exerting any additional force on the air.
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