F.3 (Combinations of Forces) QUIZ

• a
• b
• c
• d

A constant force is applied to a cart, in the same direction as its initial motion, for the entire length of a track. Which of the velocity-time graphs below best depicts the cart’s motion?

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After a sudden, brief push from a hand to get them moving, carts slow down because...

• a) The hand is no longer in contact with the cart.
• b) The force from hand runs out.
• c) Friction is acting in the opposite direction of the motion.
• d) Friction is acting in the same direction of the motion.

A student is driving along a flat stretch of highway at 70 mph. They notice when they remove their foot from the gas pedal, the car begins to slow down. Why does the car’s velocity decrease as soon as the student removes their foot from the gas pedal? Support your answer with evidence (discussions/readings/experiments conducted in class). Your answer must be articulate (well thought out and written) in complete sentence form.

Which of force-time graphs (a-d) could correspond with the velocity-time graph shown below?

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Use the velocity-time graph below to calculate the acceleration of the object from 7 to 9 seconds. Round your answer to one decimal place (the tenths place); your answer must include the correct units. (You answer should be in the form #.# x/y/z, where '#' is a whole number, and 'x', 'y', and 'z' are single letters representing a unit of measure. Don't forget to include whether the acceleration is positive or negative!)

A skateboard and a car are traveling at the same speed. The same force is applied to stop both. The skateboard will stop first. Which of the options below best supports this conclusion (that the skateboard will stop first)?

• a) Objects with greater mass have smaller resistance to changes in speed.
• b) Objects with greater mass have greater resistance to changes in speed.
• c) Objects with greater mass have less inertia.
• d) Both will stop at the same time, since the same force is applied.

An object is traveling at a constant speed. There are two equal-magnitude forces acting on the object in opposite directions. What will happen to the speed of the object as time passes?

• The object will increase in speed.
• The object will decrease in speed.
• The object will continue to travel at a constant speed.
• We cannot determine with the information given.

The mass of the box shown below is 5 kg. Given the forces shown acting on the box in the force diagram below, what will be the acceleration of the box? Assume that left is the “negative” direction.

• – 40 m/s 2
• 0.025 m/s 2
• – 0.025 m/s 2
• 40 m/s 2
• 240 m/s 2