Study Guide: Motion and Forces Unit

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Study Guide: Motion and Forces Unit

Name: ______Core: ______

STUDY GUIDE: MOTION AND FORCES UNIT

You should be able to explain how the motion of an object can be described by its position, direction of motion, and speed with respect to some other object.

Position, Distance, and Displacement Practice Problems:

Use the number line to answer questions 1-3.

  1. What is the position of each object? Heart ______Cross: ______Diamond: ______
  2. What is the distance between the heart and the diamond? ______
  3. If the diamond moved to the heart’s position, and then to the cross’s position, what is its displacement? ______

Use the number line below to answer to help answer questions 4-6. Freddy the cat started at the -3 meter position. He then walked to other locations. Mark each new location with the letter for that part.

  1. What was Freddy’s total distance traveled? ______
  2. What was Freddy’s total displacement? ______
  3. Why is Freddy’s total displacement and total distance traveled different?

Speed Practice Problems:

  1. What is the equation for speed?
  1. How are speed and velocity different?
  1. A car travels 300 km in 6 hours. What is the average speed of the car (in km/h)? Show your work.
  1. What is the speed of a jet plane that flies 7200 km in 9 hours (in km/h)? Show your work.
  1. A storm is moving toward your house at a speed of 20 km/h. It is now 60 km away from your house. How many hours will it take the storm to reach your house if it continues to travel at this speed? Show your work.
  1. A swimmer can swim at a speed of 2.8 m/s in 6 minutes. What distance will she cover in that time? (Hint: How many seconds are in a minute??) Show your work.
  1. What is the average speed of a walker who walk 500 m in 400 seconds? Show your work.

Velocity and Acceleration

  1. What is acceleration?
  1. Which of the following scenarios show acceleration? ______

a)A cyclist travels at a constant speed of 12 mph in a straight line.

b)A plane starts to slow down as it descends.

c)A runner changes direction.

d)A parked car.

  1. Draw a speed-time graph showing acceleration from AB, deceleration from BC, and a constant speed from CD. Label your axis and each point on the graph!

You should be able to explain the effects of balanced and unbalanced forces acting on an object (including friction, gravity and magnets).

Balanced and Unbalanced Forces Practice Problems:

What kind of force (balanced or unbalanced) is acting on the object or objects in each of the scenarios below?

  1. A magnet is sitting on a table and there are no other objects around it. ______
  2. The north poles of two magnets are close enough to each other to repel. ______
  3. A soccer player kicks a ball. ______
  4. A chair is in a room. ______
  5. A boy trips on his way in to class. ______
  6. Two men push a crate in opposite directions with 50 N of force. ______
  7. Two men push a crate in the same direction with 100 N of force. ______

What is the net force and the direction of movement in each scenario below?

  1. Two tugboats are moving a barge. Tugboat Little John exerts a force of 3000N to the left. Tugboat Big Sue exerts a force of 5000 N in the same direction.

Net force: ______Direction: ______

  1. Now suppose Tugboat Little John exerts a force of 2000 N pushing the barge left and Tugboat Big Sue exerts a force of 500 N to the right.

Net force: ______Direction: ______

  1. Both tugboats are exerting a force on the barge but the barge doesn’t move. What is the net force acting on the barge? ______

Gravity Review Questions

  1. As an object falls, its velocity changes at a rate of ______. What is this an example of? ______
  2. True or False: Regardless of the object’s mass, all objects fall at the same rate of acceleration due to gravity: ______
  3. True or False: The weight of an object affects how fast it falls: ______.
  4. What is the total force of an object if it weighs 30 kg? (Hint: Refer to Newton’s 2nd Law of Motion).

Newton’s Laws Review Questions:

Each of the items below is represented by one of Newton’s Laws of Motion. Write a 1, 2, or 3 for each of the following to indicate if it is Newton’s 1st Law, Newton’s 2nd Law, or Newton’s 3rd Law.

  1. A climber pulls down on a rope causing his body to rise up along the rope. ____
  2. Force = Mass x Acceleration ____
  3. Two bumper cars collide into each other and each car jolts backwards. ____
  4. When you give your friend a lift on your bike you have to pedal harder and faster to keep the same speed (and acceleration) as you had before you were on your bike alone. ____
  5. For every action there is an equal and opposite reaction. _____
  6. A smaller cannon ball leaves a cannon much faster than a heavier, larger cannon ball fired from the same cannon. _____
  7. When you are standing in a subway train, and the train suddenly stops, your body continues to go forward. ____
  8. An object at rest will stay at rest unless acted upon by an unbalanced force. _____
  9. It is much easier to carry your backpack when it is empty rather than when it is full of books. ____
  10. A boy is going down a slide. As he reaches the bottom, friction causes him to slow down and come to a stop. _____
  11. As the wheels of a drag racing car smoke and spin backwards, they eventually begin to grip the race track and push backwards on the road. In turn, the road reacts by pushing the wheels forward. ____
  12. When you throw a bowling ball out of a canoe, the bowling ball moves forward and the canoe moves backward. ___
  13. An object in motion tends to stay in motion unless acted upon by an unbalanced force. ____
  14. A basketball sits in the ball cage in the gym. It remains motionless. ____

You should be able to illustrate the motion of an object using a graph to show a change in position over a period of time.

Draw distance time graphs below for the following scenarios:

  1. An object moves away from its initial position at a constant speed.
  1. A runner jogs at a constant pace, stops to check his time, then runs back home.

styleYou should also be able to Interpret distance versus time graphs for constant speed and variable motion. Interpret the graph below and answer each question.

  1. How many times did the object stop? _____
  2. What is the object’s speed at 4 minutes?
  1. Describe what is happening between minutes 6 to 10.
  1. Create a story describing what is happening in the graph. Be sure to express what time/minutes each part of the story is.
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