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chapter 7 physics
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Gravity
Terms in this set (21)
When an object is moving with uniform circular motion, the centripetal acceleration of the object
a. is circular.
b. is perpendicular to the plane of motion.
c. is zero.
d. is directed toward the center of motion.
d is directed toward the center of motion.
What term describes a change in the speed of an object in circular motion?
a. tangential speed
b. tangential acceleration
c. centripetal acceleration
d. centripetal force
b tangential acceleration
The centripetal force on an object in circular motion is
a. perpendicular to the plane of the object's motion.
b. in the plane of the object's motion and perpendicular to the tangential speed.
c. in the plane of the object's motion and in the same direction as the tangential speed.
d. in the plane of the object's motion and in the direction opposite the tangential speed.
b in the plane of the object's motion and perpendicular to the tangential speed.
A child rides a bicycle in a circular path with a radius of 2.0 m. The tangential speed of the bicycle is 2.0 m/s.
The combined mass of the bicycle and the child is 43 kg.
What is the magnitude of the bicycle's centripetal acceleration?
a. 1.0 m/s2
b. 2.0 m/s2
c. 4.0 m/s2
d. 8.0 m/s2
b 2.0 m/s2
When a car makes a sharp left turn, what causes the passengers to move toward the right side of the car?
a. centripetal acceleration
b. centripetal force
c. centrifugal force
d. inertia
d inertia
If you lift an apple from the ground to some point above the ground, the gravitational potential energy in the
system increases. This potential energy is stored in
a. the apple.
b. Earth.
c. both the apple and Earth.
d. the gravitational field between Earth and the apple.
d the gravitational field between Earth and the apple.
In this text, which of the following symbols represents gravitational field strength?
a. F
b. G
c. g
d. F
c g
Which of the following equations expresses Newton's law of universal gravitation?
fg=gm1m2/r^2
Two small masses that are 10.0 cm apart attract each other with a force of 10.0 N. When they are 5.0 cm apart,
these masses will attract each other with what force?
(G = 6.673 × 10 N•m /kg )
a. 5.0 N
b. 2.5 N
c. 20.0 N
d. 40.0 N
d 40.0 N
In the figure above, according to Kepler's laws of planetary motion,
a. A = A .
b. Δt > Δt .
c. if Δt = Δt , then the orbit is circular.
d. if Δt = Δt , then A = A .
d
The equation for the speed of an object in circular orbit is . What does m represent in this
equation?
a. the mass of the sun
b. the mass of Earth
c. the mass of the central object
d. the mass of the orbiting object
c the mass of the central object
How would the speed of Earth's orbit around the sun change if Earth's distance from the sun increased by 4
times?
a. It would increase by a factor of 2.
b. It would increase by a factor of 4.
c. It would decrease by a factor of 2.
d. The speed would not change.
c It would decrease by a factor of 2.
When an astronaut in orbit experiences apparent weightlessness,
a. no forces act on the astronaut.
b. no gravitational forces act on the astronaut.
c. the net gravitational force on the astronaut is zero.
d. the net gravitational force on the astronaut is not balanced by a normal force.
d the net gravitational force on the astronaut is not balanced by a normal force.
Which of the following quantities measures the ability of a force to rotate or accelerate an object around an
axis?
a. axis of rotation
b. lever arm
c. tangential force
d. torque
d torque
Where should a force be applied on a lever arm to produce the most torque?
a. closest to the axis of rotation
b. farthest from the axis of rotation
c. in the middle of the lever arm
d. It doesn't matter where the force is applied.
b farthest from the axis of rotation
Suppose a doorknob is placed at the center of a door. Compared with a door whose knob is located at the edge,
what amount of force must be applied to this door to produce the torque exerted on the other door?
a. one-half as much
b. two times as much
c. one-fourth as much
d. four times as much
b two times as much
If the torque required to loosen a nut on a wheel has a magnitude of 40.0 N•m and the force exerted by a
mechanic is 133 N, how far from the nut must the mechanic apply the force?
a. 1.20 m
b. 15.0 cm
c. 30.1 cm
d. 60.2 cm
c 30.1 cm
What kind of simple machine are you using if you pry a nail from a board with the back of a hammer?
a. a wedge
b. a pulley
c.
d. a screw
c a lever
Which of the following is not a valid equation for mechanical advantage?
MA=Wout/Win
An iron bar is used to lift a slab of cement. The force applied to lift the slab is 4.0 × 10 N. If the slab weighs
6400 N, what is the mechanical advantage of the bar?
a. 1.6
b. 16
c. 6000
d. 6.3%
b 16
A box weighing 210 N is pushed up an inclined plane that is 2.0 m long. A force of 140 N is required. If the
box is lifted 1.0 m, what is the efficiency of the inclined plane?
a. 33%
b. 50%
c. 67%
d. 75%
d 75
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