# Lesson 2 : The Work - Energy Theorem

20 Questions | Total Attempts: 620  Settings  This lesson tackles about Internal vs. External Forces , The Work-Energy Connection and some Bar Chart Illustrations.

• 1.
A ball falls from a height of 2 meters in the absence of air resistance.
• A.

KE to PE

• B.

PE to KE

• 2.
A skier glides from location A to location B across a friction free ice.
• A.

KE to PE

• B.

PE to KE

• 3.
A baseball is traveling upward towards a man in the bleachers.
• A.

KE to PE

• B.

PE to KE

• 4.
A bungee cord begins to exert an upward force upon a falling bungee jumper.
• A.

KE to PE

• B.

PE to KE

• 5.
The spring of a dart gun exerts a force on a dart as it is launched from an initial rest position.
• A.

KE to PE

• B.

PE to KE

• 6.
A 1000-kg car traveling with a speed of 25 m/s skids to a stop. The car experiences an 8000 N force of friction. Determine the stopping distance of the car.
• A.

39.1 m

• B.

45.2 m

• 7.
At the end of the Shock Wave roller coaster ride, the 6000-kg train of cars (includes passengers) is slowed from a speed of 20 m/s to a speed of 5 m/s over a distance of 20 meters. Determine the braking force required to slow the train of cars by this amount.
• A.

65 657 N

• B.

56 250 N

• 8.
A shopping cart full of groceries is sitting at the top of a 2.0-m hill. The cart begins to roll until it hits a stump at the bottom of the hill. Upon impact, a 0.25-kg can of peaches flies horizontally out of the shopping cart and hits a parked car with an average force of 500 N. How deep a dent is made in the car (i.e., over what distance does the 500 N force act upon the can of peaches before bringing it to a stop)?
• A.

0.0098 m

• B.

0.78 m

• 9.
Consider the falling and rolling motion of the ball in the following two resistance-free situations. In one situation, the ball falls off the top of the platform to the floor. In the other situation, the ball rolls from the top of the platform along the staircase-like pathway to the floor. For each situation, indicate what types of forces are doing work upon the ball. Indicate whether the energy of the ball is conserved and explain why. Finally, fill in the blanks for the 2-kg ball.
• A.

All the kinetic energy of the ball is in the form of translational kinetic energy.

• B.

Insufficient amount of knowledge.

• 10.
There is a relationship between work and mechanical energy change. Whenever work is done upon an object by an external or nonconservative force, there will be a change in the___________ of the object.
• A.

Internal forces

• B.

Total mechanical energy

• 11.
There is a relationship between work and mechanical energy change. Whenever work is done upon an object by an external or nonconservative force, there will be a change in the total mechanical energy of the object. If only internal forces are doing work (no work done by external forces), there is no change in total mechanical energy; the total mechanical energy is said to be "conserved."
• A.

True

• B.

False

• 12.
The equation states that the initial amount of total mechanical energy (TMEi) plus the work done by external forces (Wext) is equal to the final amount of total mechanical energy (TMEf).
• A.

True

• B.

False

• 13.
Treat work-energy problems as mere mathematical problems.
• A.

True

• B.

False

• 14.
As the object moves from point A to point D across the surface, the sum of its gravitational potential and kinetic energies ____.
• A.

Decreases, only

• B.

Increases and then decreases

• C.

Decreases and then increases

• D.

Remains the same

• 15.
The object's kinetic energy at point C is less than its kinetic energy at point ____.
• A.

A only

• B.

A, D, and E

• C.

B only

• D.

D and E

• 16.
The object will have a minimum gravitational potential energy at point ____.
• A.

A

• B.

B

• C.

C

• D.

None of the above.

• 17.
In constructing work-energy bar charts, one of the procedure is to analyze the initial and final states of the object in order to make decisions about the presence or absence of the different forms of energy.
• A.

True

• B.

False

• 18.
In constructing work-energy bar charts, one of the procedure is to analyze the forces acting upon the object during the motion to determine if external forces are doing work and whether the work (if present) is positive or negative.
• A.

True

• B.

False

• 19.
In constructing work-energy bar charts, one of the procedure is to construct bars on the chart to illustrate the presence and absence of the various forms of energy for the initial and final state of the object; the exact height of the individual bars is not important; what is important is that the sum of the heights on the left of the chart is balanced by the sum of the heights on the right of the chart
• A.

True

• B.

False

• 20.
If only internal forces are doing work (no work done by external forces), there is no change in total mechanical energy; the total mechanical energy is said to be conserved. Because external forces are capable of changing the total mechanical energy of an object, they are sometimes referred to as nonconservative forces. Because internal forces do not change the total mechanical energy of an object, they are sometimes referred to as conservative forces.
• A.

True

• B.

False

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