Physics C Questions and Answers
An object of mass m is lifted at constant velocity a vertical distance H in time T.
The power supplied by the lifting force is
mgH/T
A system consists of two objects having masses m1 and m2 (m1 < m2). The
objects are connected by a massless string, hung over a pulley as shown above,
and then released. When the object of mass m2 has descended a distance h, the
potential energy of the system has decreased by
(m2 - m1)gh
The following graphs, all drawn to the same scale, represent he net force F as a
function of displacement x for an object that moves along a straight line. Which
graph represents the force that will cause the greatest change in the kinetic
energy of the object from x = 0 to x = X1?
LOOK AT PICTURE
A person pushes a box across a horizontal surface at a constant speed of 0.5
meter per second. The box has a mass of 40 kilograms, and the coefficient of
sliding friction is 0.25. The power supplied to the box by the person is
50 W
If a particle moves in such a way that its position x is described as a function of
time t by x=t^(3/2), then its kinetic energy is proportional to
t
From the top of a 70-meter-high building, a 1-kilogram ball is thrown directly
downward with an initial speed of 10 meters per second. If the ball reaches the
ground with a speed of 30 meters per second, the energy lost to friction is most
nearly
300J
A pendulum consists of a ball of mass m suspended at the end of a massless
cord of length L as shown above. The pendulum is drawn aside through an angle
of 60 degrees with the vertical and released. At the low point of its swing, the
speed of the pendulum ball is
Sqrt(gL)
A rock is lifted for a certain time by a force F that is greater in magnitude than the
rock's weight W. The change in kinetic energy of the rock during this time is
equal to the
Work done by the net force (F - W)
A 10-kilogram body is constrained to move along the x-axis. The potential energy
U of the body in joules is given as a function of its position x in meters by
U(x) = 6x^2 - 4x + 3
The force on the particle at x = 3 meters is
32N in -x direction
A ball is thrown upward. At a height of 10 meters above the ground, the ball has a
potential energy of 50 joules (with potential energy equal to zero at ground level)
and is moving upward with a kinetic energy of 50 joules. Air friction is negligible.
The maximum height reached by the ball is most nearly
20m
, During a certain time interval, a constant force delivers an average power of 4
watts to an object. If the object has an average speed of 2 meters per second and
the force acts in the direction of motion of the object, the magnitude of the force
is
2N
A weight lifter lifts a mass m at constant speed to a height h in time t. How much
work is done by the weight lifter?
mgh (NOT mgh/t)
A conservative force has the potential energy function U(x), shown by the graph
above. A particle moving in one dimension under the influence of this force has
kinetic energy 1.0 joule when it is at position x1. Which of the following is a
correct statement about the motion of the particle?
It cannot reach either x0 or x2
When an object is moved from rest at point A to rest at point B in a gravitational
field, the net work done by the field depends on the mass of the object and
the positions of A and B only
A force F is exerted by a broom handle on the head of the broom, which has mass
m. The handle is at an angle theta to the horizontal, as shown above. The work
done by the force on the head of the broom as it moves a distance d across a
horizontal floor is
Fd cos theta
A spring has a force constant 100 N/m and an unstretched length of 0.07 m. One
end is attached to a post that is free to rotate in the center of a smooth table, as
shown in the top view above. The other end is attached to a 1 kg disc moving in
uniform circular motion on the table, which stretches the spring by 0.03 m.
Friction is negligible. What is the work done on the disc by the spring during one
full circle?
0J
[Question refers] to the following graph, which represents a hypothetical
potential energy curve for a particle of mass m.
GRAPH
If the particle is released from rest at position r0, its speed at position 2r0 is most
nearly
Sqrt (4U0 / m)
[Question refers] to the following graph, which represents a hypothetical
potential energy curve for a particle of mass m.
GRAPH
If the potential energy energy function is given by U(r) = br^(-3/2) + c, where b and
c are constants, which of the following is an expression for the force on the
particle?
3b/2 r ^ (-5/2)
A frictionless pendulum of length 3 m swings with an amplitude of 10 degrees. At
its maximum displacement, the potential energy of the pendulum is 10J. What is
the kinetic energy of the pendulum when its potential energy is 5J?
5J
An object of mass m is lifted at constant velocity a vertical distance H in time T.
The power supplied by the lifting force is
mgH/T
A system consists of two objects having masses m1 and m2 (m1 < m2). The
objects are connected by a massless string, hung over a pulley as shown above,
and then released. When the object of mass m2 has descended a distance h, the
potential energy of the system has decreased by
(m2 - m1)gh
The following graphs, all drawn to the same scale, represent he net force F as a
function of displacement x for an object that moves along a straight line. Which
graph represents the force that will cause the greatest change in the kinetic
energy of the object from x = 0 to x = X1?
LOOK AT PICTURE
A person pushes a box across a horizontal surface at a constant speed of 0.5
meter per second. The box has a mass of 40 kilograms, and the coefficient of
sliding friction is 0.25. The power supplied to the box by the person is
50 W
If a particle moves in such a way that its position x is described as a function of
time t by x=t^(3/2), then its kinetic energy is proportional to
t
From the top of a 70-meter-high building, a 1-kilogram ball is thrown directly
downward with an initial speed of 10 meters per second. If the ball reaches the
ground with a speed of 30 meters per second, the energy lost to friction is most
nearly
300J
A pendulum consists of a ball of mass m suspended at the end of a massless
cord of length L as shown above. The pendulum is drawn aside through an angle
of 60 degrees with the vertical and released. At the low point of its swing, the
speed of the pendulum ball is
Sqrt(gL)
A rock is lifted for a certain time by a force F that is greater in magnitude than the
rock's weight W. The change in kinetic energy of the rock during this time is
equal to the
Work done by the net force (F - W)
A 10-kilogram body is constrained to move along the x-axis. The potential energy
U of the body in joules is given as a function of its position x in meters by
U(x) = 6x^2 - 4x + 3
The force on the particle at x = 3 meters is
32N in -x direction
A ball is thrown upward. At a height of 10 meters above the ground, the ball has a
potential energy of 50 joules (with potential energy equal to zero at ground level)
and is moving upward with a kinetic energy of 50 joules. Air friction is negligible.
The maximum height reached by the ball is most nearly
20m
, During a certain time interval, a constant force delivers an average power of 4
watts to an object. If the object has an average speed of 2 meters per second and
the force acts in the direction of motion of the object, the magnitude of the force
is
2N
A weight lifter lifts a mass m at constant speed to a height h in time t. How much
work is done by the weight lifter?
mgh (NOT mgh/t)
A conservative force has the potential energy function U(x), shown by the graph
above. A particle moving in one dimension under the influence of this force has
kinetic energy 1.0 joule when it is at position x1. Which of the following is a
correct statement about the motion of the particle?
It cannot reach either x0 or x2
When an object is moved from rest at point A to rest at point B in a gravitational
field, the net work done by the field depends on the mass of the object and
the positions of A and B only
A force F is exerted by a broom handle on the head of the broom, which has mass
m. The handle is at an angle theta to the horizontal, as shown above. The work
done by the force on the head of the broom as it moves a distance d across a
horizontal floor is
Fd cos theta
A spring has a force constant 100 N/m and an unstretched length of 0.07 m. One
end is attached to a post that is free to rotate in the center of a smooth table, as
shown in the top view above. The other end is attached to a 1 kg disc moving in
uniform circular motion on the table, which stretches the spring by 0.03 m.
Friction is negligible. What is the work done on the disc by the spring during one
full circle?
0J
[Question refers] to the following graph, which represents a hypothetical
potential energy curve for a particle of mass m.
GRAPH
If the particle is released from rest at position r0, its speed at position 2r0 is most
nearly
Sqrt (4U0 / m)
[Question refers] to the following graph, which represents a hypothetical
potential energy curve for a particle of mass m.
GRAPH
If the potential energy energy function is given by U(r) = br^(-3/2) + c, where b and
c are constants, which of the following is an expression for the force on the
particle?
3b/2 r ^ (-5/2)
A frictionless pendulum of length 3 m swings with an amplitude of 10 degrees. At
its maximum displacement, the potential energy of the pendulum is 10J. What is
the kinetic energy of the pendulum when its potential energy is 5J?
5J
