Unit 2 Review Motions and Forces Name:______Period :____

Study Guide

Use the textbook (3.2-3.3 and Ch 4) to answer the following questions.

  1. What is acceleration and how do you calculate it?
  1. Does an object experiencing constant acceleration have a speed that is changing? Explain.
  1. List the three kinematics equations that are used for chapter 3.
  1. A car travels at a constant rate from 15 m/s to 25 m/s while going a distance of 125 m. How long does it take to achieve this speed? (You will use 2 equations to solve this)
  1. A car travels on a racetrack at 44 m/s it slows to 22 m/s over 11 seconds. How far does it move during this time? ( You will use 2 equations to solve this)
  1. What is the difference between weight and mass?
  1. A man runs at a velocity of 4.5 m/s for 15 min. He then begins to go up a steep hill and decelerates at a constant rate of 0.05 m/s2 for 90 seconds and comes to a stop. How far did he run? (Including the original 15 minute run)
  1. What is free fall? What are the force(s) acting on an object in free fall?
  1. What is terminal velocity?
  1. A construction worker drops a brick from a high scaffold. What is the velocity of the brick after 4 seconds? How far does the brick fall during the first four seconds?
  1. A student drops a ball from a window 3.5 m above the sidewalk, How fast is it going when it hits the sidewalk. Assume terminal velocity is not reached.
  1. You flip a coin. The coin goes straight up. If the coin reaches a height of 0.25 m above where you flipped it, what was the original speed? If you catch the coin at the same spot you released it, how long was it in the air?
  1. List Newton’s Three Laws of motion. You need to know these.

Newton’s Laws Study Problems

Newton’s Second and Third Laws on a level surface without friction

  1. What is the normal force? In what situations do you have a normal force? In what situations do you not have a normal force? In Figure 1 draw the normal force vector.
  1. Weight is equal to mass times the gravity. In what situations do we have weight? In Figure 1 draw the weight vector and write the formula next to it.

Figure 1

For this figure we have now drawn all of the forces (ignoring friction). Now we will apply Newton’s second law to the figure above. Note that there is already a force of 50 Newtons action on the box.

  1. Find the weight of the 5 Kg box.
  1. Apply Newton’s second law to the force acting in the x-direction in Figure 1. List the x-direction force. Do not substitute any numbers for variables at this point.
  1. Apply Newton’s second law to all of the forces acting in the y-direction in Figure 1. List all the y-direction forces. Do not substitute any numbers for variables at this point.
  1. What do you know about the acceleration in the y direction (ay)?
  1. Find the Normal force of the block. To do this, use the relationship you just talked about in questions 18 and 19.
  1. Find the acceleration of the block in the x direction. To do this, use the equations you just found in question 17.

Newton’s Second and Third Laws with Tension

  1. What is tension? In what problems do we apply tension to? In Figure 2 draw the force vectors representing tension.

= 7 kg

Figure 2

  1. In Figure 2 what other forces are acting on the blocks? Draw these forces on the diagram above.
  1. Apply NII to the first block, m1. Do this by first drawing a separate free-body diagram of m1 below.
  1. Apply NII to the second block, m2. Do this by first drawing a separate free-body diagram of m2 below.
  1. Based on the FBD for both masses, what do we know about the accelerations in the x directions? What do we know about the accelerations in the y directions?
  1. Based on your answers in #14-16, write the relationship between the forces present for each mass. Now, solve each equation for the tension in each rope. Based on your answer in #16, set the appropriate equations equal to each other.

Newton’s Second and Third Laws with a Normal Force

  1. Label all the forces present in the stack of blocks below.
  1. Before doing any calculations, predict which Normal force will be the greatest. Explain your reasoning.
  1. List the opposing force pairs. Calculate the value of each force. Show your work below. Was your prediction correct?

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