Name:______Block: ____Date: ____/____/____

IP 670

“Introduction to Forces” Unit Review

Force Identification

Forces to Choose From:

  • Normal
  • Friction
  • Gravity
  • Air Resistance
  • Tension
  • Spring or Elastic
  1. What two forces are exerted on the leaf while it falls? ______and ______.
  1. What force does the rope exert on the people? ______
  1. The weight of an object is a measure of the force of ______.
  1. When you push a chair, what force (between the floor and the chair) opposes your push? ______

Multiple Choice Review

______1.All of the following are forces except

a. gravity. b. mass. c. magnetism. d. friction.

______2. The force that opposes the downward motion of a falling object falling through air is called

a. pressure. b. terminal velocity. c. air resistance. d. friction.

______3.Hail falls to the ground because of the force of

a. magnetism. b. friction. c. gravity. d. electricity.

______4. Sand is sometimes spread on an icy surface in order to

a. decrease friction. b. increase air resistance.

c. decrease air resistance. d. increase friction.

______5. As you push a chair, friction equal to a force of 5 N pushes in the opposite direction. How will the force needed to push the chair at a constant speed compare to the force of friction?

a. The comparison depends on the type of friction.

b. The force will be less.

c. The force will be equal to the force of friction.

d. The force will be greater.

______6. The weight of an object tells you

a. how large the object is. b. how heavy the object is.

c. how tall the object is. d. the shape of the object.

______7.What does a spring scale measure?

a. volume b. temperature c. weight d. distance

______8.An astronaut on the Moon dropped a 2-N rock and 7-N rock from the same height at the same time. Which will hit the surface of the Moon first?

a. 2-N rock b. 7-N rock

c. Neither will hit the Moon. d. They will hit at the same time.

______9.If an object is said to be in equilibrium, then the forces acting on the object must be:

a. balancedb. unbalanced

c. changing d. zero

Written Response Answer the following questions using complete sentences.

  1. EXPLAIN: If two groups of people are in a tug of war, what must happen to the forces on the rope for the rope to A.) stay in place? B.) for it to move in a certain direction?

Explain your answers, being sure to use the following words/phrases:

  • balanced forces
  • unbalanced forces
  • equilibrium.
  • For the rope to stay in place:
  1. For the rope to move in a certain direction:
  1. Describe: Friction can make it difficult in our daily lives. What is the difference between static friction and kinetic friction when you want to move the heavy lab table in the classroom.

Interacting or Not?

For each situation, write yes or no on the line to left.

  • Yes means that the two objects are interacting (exerting forces on each other.)
  • No means that the two objects are not interacting.

______1.The top book and the middle book.

______2.The top book and the bottom book.

______3.The top book and the earth.

A few basic facts about forces

Word Bank:

  • Newton
/
  • Push
/
  • Pull

  • Balanced
/
  • Unbalanced
/
  • Equilibrium

  1. A force is a ______or a ______.
  2. Forces are measured in units of ______.
  3. ______forces result in changes in motion.
  4. ______forces result in no changes in motion.
  5. When forces are balanced, the object is said to be in ______.

Spring Scales

Read the measurements on the following spring scales:

______N / ______N / ______N / ______N

Averages:

Calculate the average (mean) for each set of data:

Trial / Data / Average
A / 5.0N, 5.2N, 4.7N, 4.85N
B / 15N, 16N, 13N, 18N, 16.5N

Free-Body (Force) Diagrams.

For each of the following situations, identify the forces and the sources.

  1. A star is popping out of a box. Identify the forces acting on the star.
Force / Source
1
2
  1. A boy is pulling a sled. The sled is being dragged to the left. Identify the forces on the sled. (The rope is pulling the sled to the left.)
Force / Source
1
2
3
4 / Tension / Rope

MCAS Questions: Questions 1-8

_____ 1.The pull of gravity on Earth is a direct result of the

  1. mass of Earth.
  2. magnetic field of Earth.
  3. rotation of Earth on its axis.
  4. weight of Earth’s atmosphere.

_____ 2.On Earth, Johanna weighs 100 lbs. She calculated what her weight would be at several other locations in the solar system. The results are shown in the table below.

Location in / Weight
Solar System / (lbs.)
Venus / 90
Earth / 100
Moon / 16
Mars / 40
Jupiter / 260

Which of the following statements is best supported by the information in the table?

  1. Venus has more gravitational force than Earth.
  2. Mars has less gravitational force than the Moon.
  3. Earth has four times the gravitational force of Mars.
  4. Jupiter has more than twice the gravitational force of Earth.

_____ 3.The force of gravity on an object depends primarily on the object’s

  1. density.
  2. mass.
  3. momentum.
  4. volume.

_____ 4.Two forces act on the box shown below. A 4 N force acts to the right and a 6 N force acts to the left. What is the net force acting on the box?

  1. 10 N to the right
  2. 10 N to the left
  3. 2 N to the right
  4. 2 N to the left

_____ 5.The illustration below shows a 2-ton elephant balancing on a tree stump. Which of the following statements must be accurate?

  1. The weight of the tree stump is greater than 2 tons.
  2. A 4-ton force on the ground spreads out in all directions.
  3. The tree stump is exerting a 2-ton force upward on the elephant.
  4. The downward force on the ground under the tree stump is 4 tons.

_____ 6.The forces acting on a skateboarder moving at a constant velocity along a sidewalk are shown in the figure below.

Which of the following is the net force on the skateboarder?

  1. 0 N
  2. 70 N
  3. 670 N
  4. 1270 N

_____ 7.A hot air balloon exerts a force of 1200 N while lifting a load of 800 N. Which free-body force diagram below depicts the forces involved?

/ _____ 8.An upward force of 150 N is applied to a box weighing 70 N. Which of the following is the free-body force diagram for this situation?