Work and Energy Practice

A skateboarder of mass M initially moves with velocity V on a horizontal path. The skateboarder travels a distance D as she slows to a stop. Assume friction is constant. What variable(s) would you need to calculate Kinetic Energy?

• Mass

• Velocity

• Height

• Potential Energy

A new skateboarder of mass M initially moves with velocity 4V on a horizontal path. The skateboarder travels a new distance as she slows to a stop. Assume friction is constant. How does this new distance compare to a skateboarder with velocity V?

• 2D

• 4D

• 8D

• 16D

Answer explanation

Stopping distance has a squared relationship with velocity :)

A new skateboarder of mass M initially moves with velocity V on a horizontal path. The skateboarder travels a new distance as she slows to a stop because friction is now doubled. How does this new distance compare to when we have friction F?

• 1/2D

• D

• 2D

• 4D

Answer explanation

Friction has an inverse relationship with stopping distance :)

A new skateboarder of mass 4M initially moves with velocity V on a horizontal path. The skateboarder travels a new distance as she slows to a stop. Assume friction is constant. How does this new distance compare to a skateboarder with mass M?

• 1/4D

• 1/2D

• D

• 4D

Answer explanation

Mass does not affect stopping distance because it increase the friction, but also increases the energy. Therefore, they balance out. No effect.

A new skateboarder of mass 2M initially moves with velocity 4V on a horizontal path. The skateboarder travels a new distance as she slows to a stop because friction is halved. How does this new distance compare to the original skateboarder (Mass M, velocity V, friction F)?

• 2D

• 8D

• 16D

• 32D

A student pushes a table across the floor. There is a force of friction constantly at 5 N. What is happening to the motion of the object between 35-40m?

• Speeding Up

• Slowing Down

• Constant Speed

• Turns around and slaps the student

Answer explanation

Since the force being used is smaller than the force of friction, that means we have an unbalanced force AGAINST us. Therefore, slowing down.

A student pushes a table across the floor. There is a force of friction constantly at 5 N. What is happening to the motion of the object between 0-5m?

• Speeding Up

• Slowing Down

• Constant Speed

• Absolutely Nothing... for sure

Answer explanation

Friction is still larger than our force of pushing.

A student pushes a table across the floor. There is a force of friction constantly at 5 N. What is happening to the motion of the object between 5-35m?

• Speeding Up

• Slowing Down

• Constant Speed

• Literally Everything

Answer explanation

Since our force is larger than the friction force, it means there is an unbalanced force WITH us. Therefore, speeding up.

A student pushes a table across the floor. There is a force of friction constantly at 5 N. At what point do you have the highest speed?

• 5 m

• 10 m

• 30 m

• 35 m

• None of the above

Answer explanation

Our highest speed is found when the most amount of positive work (unbalanced force WITH us) has been done. This is found at 35 m.

What is the amount of work done between 0-4 m?

• 40 J

• 30 J

• 60 J

• No clue...

Answer explanation

Area under the line of a Force x Displacement graph is how you find work.