Chapter 7 - Work and Energy
If both mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of:
27
A Hooke's law spring is compressed a distance d and is used to launch a particle of mass m vertically to a height h above its starting position. Under double the compression, the spring is now used to launch a particle of mass 2 m. How high does the second mass rise above its starting position?
2h
By how much is the energy stored in a Hooke's law spring increased when its stretch is increased from 8.00 cm to 16.0 cm?
300%
A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position. Under double the compression, the spring is now used to launch the mass. How high does the mass now rise above its starting position?
4h
A golf ball hits a wall and bounces back at 3/4 the original speed. What part of the original kinetic energy of the ball did it lose in the collision?
7/16
The work done by static friction can be:
Any of the above
If during a given physical process the only force acting on an object is friction, which of the following must be assumed in regard to the object's kinetic energy?
It cannot be determined from the information given.
In a problem using energy considerations to solve for the speed of a ball thrown from the top of a building when it strikes the ground below, where should the potential energy have its zero value?
It doesn't matter since only differences in potential energy matter in solutions.
When an object is dropped from a tower, what is the effect of the air resistance as it falls?
None of the above choices are valid
A student has to work the following problem: A block is being pulled along at constant speed on a horizontal surface a distance d by a rope supplying a force F at an angle of elevation . The surface has a frictional force acting during this motion. How much work was done by friction during this motion? The student calculates the value to be -Fdsin(theta). How does this value compare to the correct value?
The answer cannot be found until it is known whether theta is greater than, less than, or equal to 45°.
A block is projected with speed v across a horizontal surface and slides to a stop due to friction. The same block is then projected with the same speed v up an incline where is slides to a stop due to friction. In which case did the total mechanical energy of the block decrease the least?
The case on the inclined surface had the least decrease in total mechanical energy.
Three different mass projectiles are launched from the top of a building each at different angles of elevation. Each particle has the same initial kinetic energy. Which particle has the greatest kinetic energy just as it impacts with the ground?
The one with the highest mass.
Three different mass projectiles are launched from the top of a building each at different angles of elevation. Each particle has the same initial kinetic energy. Which particle has the greatest speed just as it impacts with the ground?
The one with the lowest mass.
Two blocks are released from the top of a building. One falls straight down while the other slides down a smooth ramp. If all friction is ignored, which one is moving faster when it reaches the bottom?
They both will have the same speed.
As an object is lowered into a deep hole in the surface of the earth, which of the following must be assumed in regard to its potential energy?
decrease
Which of the following is an example of a nonconservative force?
friction
A Hooke's law spring is compressed a distance d and is used to launch a mass m vertically to a height h above its starting position. Under the same compression d, the spring is now used to launch a mass of 2m. How high does this second mass rise?
h/2
A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface. As the speed of the mass increases at a constant acceleration, the power delivered to it by the force:
increases
The unit of power, watt, is dimensionally the same as:
joule/second
The SI units for k, the spring constant, are equivalent to:
kg/s^2
Which of the following is that form of energy associated with an object's motion?
kinetic
The unit of work, joule, is dimensionally the same as:
newton-meter
Which of the following is that form of energy associated with an object's location in a conservative force field?
potential
The rate at which work is done is equivalent to which of the following?
power
The quantity of work equal to one joule is also equivalent to which of the following?
watt s
The area under the force vs. displacement curve represents:
work
Is it possible for the total mechanical energy of a moving particle to be negative?
yes
