Unit 8 Study Guide Let’s check your answers!

(Study your “Newton’s 1st Law of Motion” notes, “Friction and How Things Move” notes, “Coin Caper” lab/activity, “Newton’s 2nd Law of Motion” notes, your “Acceleration and Newton’s 2nd Law: Homework”, your “Newton’s 3rd Law of Motion and Momentum” notes, your Newton’s 1st and 2nd/3rd Quiz, and think back on the “Newton’s 3rd law and Momentum” puck lab.)

1.What is Newton’s 1st law of motion?  An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion at constant velocity will continue at the same velocity unless acted on by an unbalanced force.

2.What is inertia? Objects have a tendency to resist a change in their motion.

3.Draw and label an example of an object experiencing Newton’s 1st law of motion. Will remain at rest until someone pushes it, pulls it or picks it up.

4.What are the four types of friction we discussed in class?  Static, sliding, rolling and fluid

5.Give an example for each type of friction. Don’t forget to include the surfaces the friction is occurring between. Static- flowerpot sits on a table. Bottom of pot + table. Sliding- Skidding across the gym floor on your knees. Knees+ gym floor Rolling- Wheels on the bus. Bottom of wheel + road Fluid- A skydiver. His body + air

6.When there is an applied force, which direction does friction occur? OPPOSITE WAY

7.Draw and label a picture of an object experience rolling friction. Don’t forget to include the applied force (arrow with size and direction) and the friction (arrow with size and direction).

8. What is Newton’s 2nd law of motion? What is the formula we use for Newton’s 2nd law?  An object’s acceleration is equal to the ratio of the force on that object divided by the object’s mass.  a = F/m

9. What are the three ways objects can experience acceleration? Speeding up, slowing down, changing direction (Any change in VELOCITY)

10.There are two boxes on your kitchen floor. One box is empty and the other contains your Mom’s new microwave. You apply the same force to each box. Which box will accelerate more? Explain why using Newton’s 2nd law of motion.  The empty box will accelerate more. This is because that with the same size force, a smaller mass will experience more acceleration.

11.There are two identical desks on the floor in your science classroom. You give your desk a slight push. Matt takes a running start, and shoves the desk in front of him very forcefully. Which desk will accelerate more? Explain using Newton’s 2nd law of motion.  Matt’s desk will accelerate more. This is because a large force will cause a mass to accelerate more.

12.What is Newton’s 3rd law of motion?  For every action there is an equal and opposite reaction.

13.Draw and label a diagram of an object experiencing Newton’s 3rd law of motion. Don’t forget to label the action and reaction forces with direction. Action: air rushes backwards out of balloon. Reaction: balloon shoots forwards.

14.What is the formula to calculate momentum? Momentum = mass x velocity

15.What does the law of conservation of momentum state?  Momentum cannot be created or destroyed. The loss in momentum of one object equals the gain in momentum of another object.

16.If a buffalo and a prairie dog are both running down the plain at 12 m/s, which is has more momentum? Explain why using the formula and/or law of conservation of momentum.  The buffalo has more momentum, since it has more mass. Momentum is the product of mass and velocity.

17.If an elephant and a rabbit were to experience a head on collision, what would happen? Explain using the law of conservation of momentum.  The elephant would slow down a bit, but the rabbit would be thrown backwards at a high speed. Some of the elephant’s momentum is transferred to the rabbit, and it experiences and change in its motion.

18.What is projectile motion? Why does it occur?  Projectile motion is the path an object takes when it is thrown, kicked, etc. It travels in an arc, also known as a parabola. It happens because of the push forward and up, and the downward pull of gravity.

19.Draw a diagram of an object experiencing projectile motion.

20.What shape does an object travel in during projectile motion?  A parabola.

21.Draw a picture of a person sprinting down the street to the right. Label (arrows with size and direction) at least 4 forces that are acting on the sprinter. Feet push BACK on ground. Ground pushes FORWARDS on feet. Sliding friction on feet, resisting motion. Air resistance on body. Gravity pulling down, ground pushes up.

22.What is a force? Give two examples of forces you encounter everyday.  A force is a push or pull that can cause a change in an object’s motion.  Gravity pulls you down to Earth, friction fights every motion you make.

23. What units do we use to measure force? How do we abbreviate these units? Who is the unit named after? We measure force in Newtons. Abbreviation: NNamed after Sir Isaac Newton..

24. What is net force?  The overall or total force on an object.

25.What is a balanced force? What is the net force equal to when forces are balanced? What happens to an object when forces are balanced? A balanced force is when the net force is zero and there is NO CHANGE in the object’s motion.

26.What is an unbalanced force? A force that causes an object to have a change in motion.

27. When unbalanced forces are acting in the same direction, what do we do to them (mathematically)?  Addition

28. Two people are pushing on a piano. Person A is pushing to the right with a force of 20N. Person B is pushing to the right with a force of 35N. What is the net force on the piano? What will the piano do?  The net force is 55N to the right. It will move to the right.

29.When unbalanced forces are acting in different directions, what do we do to them (mathematically)?  Subtraction

30.Two people are pushing on a desk. Person A is pushing to the right with a force of 50N. Person B is pushing to the left with a force of 25N. What is the net force on the desk? What will the desk do?  25 N to the right. The desk will move to the right.