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23 Cards in this Set

  • Front
  • Back
A stone is tied to the end of a string and swings in a circular motion. If the speed of the stone is tripled, the centripetal force of the stone will become

A. 3 times as great.
B. 1/3 as much.
C. 9 times as great.
D. 1/9 as much.
C. The centripetal force of the stone is proportional to the square of the velocity.
Which of the following units measures the weight of a body?

A. pound
B. Newton
C. kilogram
D. kg.m/s2
B. The weight of a body is a force, and newton is the unit of force.
The joule is a unit of

A. work only.
B. kinetic energy only.
C. potential energy only.
D. heat.
D. The joule is the unit of work, kinetic energy, potential energy, and heat.
Two objects with different weights are dropped at the same moment from the top of the Leaning Tower of Pisa.

A. Both objects hit the ground at the same time.
B. The heavier object hits the ground first.
C. The heavier object hits the ground last.
D. The arrival time at the ground depends on the density of each object.
A. The travel time depends on the height above ground and the acceleration of gravity, both of which are the same for both objects.
The quantity 2 m/s2 is a measure of

A. speed.
B. acceleration.
C. velocity.
D. metric volume.
B. The quantity 2 m/s2 can be thought of as 2 m/s per second; that is, speed per unit time, or acceleration.
For a car moving around a circular track at a constant speed, the acceleration is

A. away from the center of the circle.
B. towards the center of the circle.
C. in the direction of motion.
D. opposite to the direction of motion.
B. From Newton's second law of motion, the centripetal force, or the inward force necessary to maintain uniform circular motion, is the product of mass and centripetal acceleration.
A ball thrown vertically upward has an initial potential energy of 100 J and an initial kinetic energy of 700 J. At the top of the trajectory its energy in joules is

A. 100
B. 700
C. 800
D. 1,000.00
C. At the top of the trajectory the ball stops and all the kinetic energy has already been converted to potential energy. Thus the total energy is the sum of 100 and 700, or 800 J.
A simple pendulum has a frequency of oscillation f. In order to double f, the length of the pendulum should be

A. increased by a factor of 2.
B. decreased by a factor of 2.
C. increased by a factor of 4.
D. decreased by a factor of 4.
D. Since the frequency of oscillation is inversely proportional to the square root of the length of the pendulum, the length has to be decreased by a factor of 4 for the frequency to be doubled.
The velocity of a baseball 4 seconds after it is thrown vertically upward with a speed of 32.1 m/s is

A. -7.2 m/s.
B. 71.2 m/s.
C. 7.20 m/s.
D. 14.6 m/s.
A. The final velocity is the initial velocity minus four times the acceleration of gravity (9.8 m/s) or -7.14 (about 7.2) m/s
In order for a volleyball player to jump vertically upward a distance of 0.8 meters, his initial velocity must be

A. 3.92 m/s.
B. 1.96 m/s.
C. 4.27 m/s.
D. 2.15 m/s.
A. Using the expressions s=vot +1/2at2 and vf = vo + at , you obtain = 0.4 s and vo = 3.92 m/s.
The graph of velocity versus time for an object with a constant negative acceleration would be

A. a straight line with a positive slope.
B. a straight line with a negative slope.
C. a line curving upward with a positive slope.
D. a line curving downward with a negative slope.
B. Since acceleration is the time derivative of the velocity, the slope has to be constant and must also be negative since the acceleration is constant and negative.
The torque required to loosen a nut that holds a wheel on a car has a magnitude of 56 newton-meters. If a 0.35-meter lug wrench is used to loosen the nut when the angle of the wrench is 56°, the force that must be exerted at the end of the wrench is

A. 200 N.
B. 286 N.
C. 143 N.
D. 100 N.
B. Since the torque T = Fd cos q where F is the force, d is the arm, and q is the angle between the force and arm, then you can solve for F to obtain 286 N.
The gain in kinetic energy if a 400-kilogram satellite moves from a distance of 3 × 106 meters above the surface of the Earth to a point 1.50 × 106 meters above the surface is _______ J. The mass of the Earth is 5.98 × 1024 kilograms and the radius of the Earth is 6.37x106 meters.

A. -1.7 × 109
B. 3.25 × 109
C. 1.7 × 109
D. -3.25 × 109
B. K + (6.67 x 1011) (400) (5.96 x 10)/(6.37 x 106 + 3 x 106) = (6.67 x 10 -11) (400) (5.98 x 1024)/(6.37 x 106 + 1.5 x 106) or K = -3.25 x 109 J.
The speed of a baseball with a momentum of 5.8 kilograms m/s and a mass of 0.145 kilograms is

A. 0.841 m/s.
B. 1.19 m/s.
C. 36.0 m/s.
D. 40.0 m/s.
D. Since the momentum P equals the mass m times the velocity v, it follows that v = P/m = 40.00 m/s.
A 0.24-kilogram glider moving with a velocity of 0.6 m/s collides with and sticks to a 0.26-kilogram glider moving with a velocity of 0.2 m/s. The final velocity v of the two gliders is

A. 0.392 m/s.
B. 0.184 m/s.
C. 0.092 m/s.
D. -0.092 m/s.
A. Conservation of momentum requires that 0.24(0.6) + 0.26(0.2) = (0.24 + 0.26)v. Hence v = 0.392 m/s.
Two balls of different masses are thrown vertically up from the same point and at the same time. The two balls will experience the same change in

A. velocity.
B. acceleration.
C. momentum.
D. kinetic energy.
A. Acceleration will be the same for both arrows. Momentum and energy are dependent on mass and will therefore be different. Only the change in velocity will be the same for both arrows.
An arrow is shot vertically up. As the arrow approaches its maximum altitude, the amount of work done against gravity

A. increases.
B. decreases.
C. increases and then decreases.
D. remains the same.
D. The work done does not depend on time or path of travel since the deceleration of the arrow is constant.
The resistance of an object to a change of motion is determined by its

A. mass.
B. weight.
C. prior motion.
D. distance of travel.
A. The resistance to motion is a force that is determined by mass in accordance with Newton's second law.
Which of the following units is equivalent to the joule?

A. kg.m/s
B. kg.m/s2
C. kg/s2
D. kg.m2/s2
D. The joule is a unit of work that is force times distance. The force is mass times acceleration, which has the units of kg.m/s2. Hence, kg.m2/s2 is the product of the units of force and distance.
A 15-gram bullet is fired into a 3-kilogram block of plastic suspended from the ceiling by a string. As a result of the impact, the block with the bullet swings 12 centimeters above its original level. The velocity of the bullet as it strikes the block is nearly

A. 3.08 m/s.
B. 30.8 m/s.
C. 308 m/s.
D. 3,080 m/s.
C. Letting the masses of the bullet and block be m and M, and their initial velocities be u and U and their combined velocity be V, then the conversion from kinetic to potential energy requires that 1/2(m+M)V2=(m+M)gh, where h is the increment in height (12 cm). This leads to V = 1.533 m/s. The conservation of momentum requires that mu + MU = (m + M)V where U = 0. Hence, solving for u you obtain 308.258, or about 308 m/s.
An astronaut lands on Jupiter. Which of the following is true?

A. Mass increases but weight decreases.
B. Mass remains the same but weight increases.
C. Mass decreases but weight remains the same.
D. Both mass and weight decrease.
B. Mass cannot change because of changes in the gravitational acceleration, but weight changes -- and in this case increases -- since the gravitational acceleration is higher.
Ignoring air resistance, the acceleration of a person sliding down an inclined plane with a constant coefficient of kinetic friction

A. is constant.
B. increases with time.
C. decreases with time.
D. depends on the mass and shape of the person.
A. The acceleration is the ratio of the force and the mass. The mass remains the same while the net force is set by the mass, acceleration of gravity, slope of the inclined plane, and the coefficient of kinetic friction, which are all constant. Thus the acceleration remains the same.
A bicycle collides head-on with a large truck moving at the same speed. Following the collision, the bicycle and the truck stick together. Which of the two had the larger change in momentum?

A. the bicycle
B. the truck
C. both had equal change
D. none of the above
C. Since the momentum is conserved, there is no change in speed due to the collision, and the momentum of both remains the same.