physics unit 2 - extra credit

Which of the following statements is/are true? A. The total mechanical energy of a system is equally divided between kinetic and potential energy. B. Mechanical energy can be dissipated to nonmechanical forms of energy. C. The total mechanical energy of a system is constant only if nonconservative forces do work. D. The total mechanical energy of a system, at any one instant, is either all kinetic or all potential energy. E. The total mechanical energy of a system is constant only if conservative forces do work.

B. Mechanical energy can be dissipated to nonmechanical forms of energy. E. The total mechanical energy of a system is constant only if conservative forces do work.

During a certain time interval, the net work done on an object is zero joules. We can be certain that ____. A. the object was at rest at the end of this interval B. the object's final speed was the same as its initial speed C. the object was at rest during this entire interval

B. the object's final speed was the same as its initial speed When the net work done on an object is zero, there is no overall change in the object's kinetic energy.

A graph depicts force versus position. What represents the work done by the force over the given displacement? A. The work done is equal to the product of the maximum force times the maximum position. B. Work cannot be determined from this type of graph. C . The work done is equal to the area under the curve. D. The work done is equal to length of the curve. E. The work done is equal to the slope of the curve.

C . The work done is equal to the area under the curve.

If the net work done on an object is positive, what can you conclude about the object's motion? A. If the net work done on an object is positive, what can you conclude about the object's motion? B. The object is moving with a constant velocity. C. The object is speeding up. D. The object is slowing down. E. The object is at rest; its position is constant.

C. The object is speeding up.

If the net work done on an object is zero, what can you determine about the object's kinetic energy? A. The object's kinetic energy is zero. B. The object's kinetic energy is increasing. C. The object's kinetic energy is decreasing. D. The object's kinetic energy remains the same.

D. The object's kinetic energy remains the same.

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground. When he comes to a recently plowed section of road, he continues to pull the sled with the same force across the road while the road exerts a frictional force of 4 N on sled. What is the net work done on the sled while Max pulls it 5 m across the road? A. 58 J B. 7.6 J C. 78 J D. 16 J E. 38 J

E. 38 J W = ((12)cos 15 - 4) (5) =38

Two identical balls are thrown vertically upward. The second ball is thrown with an initial speed that is twice that of the first ball. How does the maximum height of the two balls compare? A. The maximum heights of the two balls are equal. B. The maximum height of the second ball is 1.41 times that of the first ball. C. The maximum height of the second ball is two times that of the first ball. D. The maximum height of the second ball is eight times that of the first ball. E. The maximum height of the second ball is four times that of the first ball.

E. The maximum height of the second ball is four times that of the first ball.

Two objects are moving at equal speed along a level, frictionless surface. The second object has twice the mass of the first object. They both slide up the same frictionless incline plane. Which object rises to a greater height? A. Object 1 rises to the greater height because it weighs less. B. Object 2 rises to the greater height because it contains more mass. C. Object 1 rises to the greater height because it possesses a smaller amount of kinetic energy. D. Object 2 rises to the greater height because it possesses a larger amount of kinetic energy. E. The two objects rise to the same height.

E. The two objects rise to the same height.

Person B does twice the work of person A, and in one-half of the time . How does the power output of person B compare to person A? A. Person B has twice the power output of person A. B. Person B has four times the power output of person A. C. Person B has the same power output as person A. D. Person B has half the power output of person A. E. Person B has eight times the power output of person A.

P = W/t B. Person B has four times the power output of person A. twice the work = 2, half the time = 2 2*2 = 4

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground. When he comes to a recently plowed section of road, he continues to pull the sled with the same force across the road while the road exerts a frictional force of 4 N on sled. If the sled's speed is 1.5 m/s as Max pulls it onto the road, what is the sled's speed after Max pulls it 5 m across the road? A. 2.5 m/s B. 2.0 m/s C. 2.8 m/s D. 6.0 m/s E. 3.2 m/s

A. 2.5 m/s W - f * d = 1/2m(2v^2-1v^2) 58-(4)(5) = 1/2(20)(v^2-1.5) 2v= 2.5

On a snowy day, Max (mass = 15 kg) pulls his little sister Maya in a sled (combined mass = 20 kg) through the slippery snow. When Max pulls on the sled with 12 N of force, directed at an angle of 15° above the ground, how much work does Max do on the sled as he pulls his sister 25 m in the snow? A. 300 J B. 11.6 J C. 77.6 J D. 290 J

A. 300 J W = Fd = Fd cos (theta) W = (12)(25)cos15 = 290 N

Which of the following statements is/are true? A. A potential energy function can be specified for a conservative force. B. The work done by a conservative force depends on the path taken. C. A conservative force permits a two-way conversion between kinetic and potential energies. D. The work done by a nonconservative force depends on the path taken. E. A potential energy function can be specified for a nonconservative force. F. A nonconservative force permits a two-way conversion between kinetic and potential energies.

A. A potential energy function can be specified for a conservative force. C. A conservative force permits a two-way conversion between kinetic and potential energies. D. The work done by a nonconservative force depends on the path taken.

Which of the following statements is/are true? A. The SI unit of power is the watt. B. Power is the rate at which work is done. C. Power is the rate at which energy is transformed. D. A person is limited in the total work he or she can do by their power output. E. The SI unit of power is the horsepower.

A. The SI unit of power is the watt. B. Power is the rate at which work is done. C. Power is the rate at which energy is transformed.

A ball is thrown straight upward. How does the sign of the work done by gravity while the ball is traveling upward compare with the sign of the work done by gravity while the ball is traveling downward? A. Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward. B. Work done by gravity is negative while the ball is traveling both upward and downward. C. Work done by gravity is positive while the ball is traveling both upward and downward. D. Work done by gravity is positive while the ball is traveling upward and negative while the ball is traveling downward.

A. Work done by gravity is negative while the ball is traveling upward and positive while the ball is traveling downward.

An object weighing 20 N moves horizontally toward the right a distance of 5.0 m. What is the work done on the object by the force of gravity? A. The work done on the object by the force of gravity is 4.0 J. B. The work done on the object by the force of gravity is 100 J. C. The work done on the object by the force of gravity is zero joules. D. The work done on the object by the force of gravity is 0.25 J. E. The work done on the object by the force of gravity is 50 J.

W= fs cos (theta) C. The work done on the object by the force of gravity is zero joules.

A person applies a horizontal 50 NN force on a crate, causing it to move horizontally at a constant speed through a distance of 10 mm. What is the net work done on the crate? A.The net work done on the crate is 5 J . B. The net work done on the crate is 500 J . C. The net work done on the crate is 250 J . D. The net work done on the crate is 0.2 J . E. The net work done on the crate is zero joules.

W=Fs cos(theta) F = ma E. The net work done on the crate is zero joules. Constant speed = acceleration is zero

A motorcycle drives up a steeply inclined ramp. The work done on the motorcycle by the Earth's gravitational force is ____. A. Postive B. Negative C. zero

When an object's displacement has a component in a direction opposite that of a given force, that force does negative work on the object. B. Negative

Two identical cars are driving in opposite directions at the same speed. Their kinetic energies have ____. A. different magnitudes, but the same sign B. the same magnitude, but opposite signs C. the same magnitude and sign D. different magnitudes and opposite signs

The kinetic energy of a moving object is always positive, regardless of the direction it is moving in, or the coordinate system used. C. the same magnitude and sign