Reviewing Motion & Forces

1. Reviewing Motion & Forces

2. 1. How do scientists express force? • Newton (N)

3. 2. What is net force? • The total combination of forces on an object. • Same direction (add) • Different direction (subtract)

4. 3. How are balanced and unbalanced forces different? Give an example for each. • Balanced forces mean net force = zero. • Unbalanced forces mean the net force does NOT equal zero.

5. 4. Name and describe each type of Kinetic friction. • Sliding Friction is two surfaces rubbing back and forth against each other. (ice skating) • Rolling Friction is anything circular that rolls over another surface. (bike)

6. 5. What are some ways of increasing and decreasing friction? • Increasing friction can be done by making the surface rougher (like putting sand on an icy sidewalk) • Decreasing friction can be done by using a lubricant (oil) or making the surface smooth (sanding a piece of wood)

7. 6. What is the difference between kinetic and static friction? • Kinetic = motion • Static = no motion

8. 7. State the law of universal gravitation. Why is it called universal? • Gravity increases as mass increases (more mass = more gravity). • Gravity decreases as distance increases (more distance = less gravity). • It is universal because it applies to every situation involving gravity!

9. 8. How can you illustrate the two parts of the Law of Gravitation? • The closer you get to Earth the more its gravitational force pulls you down. • Jupiter has more mass than Earth; therefore Jupiter has a greater gravitational force.

10. 9. Who was Sir Isaac Newton? • He was an English scientist who lived in the 1600s and studied physics, mathematics, and astronomy.

11. 10. If Venus and Earth have the same mass, why is the gravity between Venus and the sun greater that the gravity between Earth and the sun? • Think about the Universal Law of Gravity… • Which planet is closer to the sun? • Venus is closer to the sun so the sun’s gravity affects Venus more than Earth.

12. 11. Explain why weight is expressed in Newtons (N)? • Weight is the measure of gravitational pull. • Gravity is a force. • All forces are measured in Newtons.

13. 12. What is the difference between weight and mass? • Weight is the measure of gravity, unit is Newtons, use a spring scale. • Mass is how much matter/stuff an object contains, unit is the gram, use a triple beam balance.

14. 13. What does Newton’s first law say? • An object in motion will stay in motion, an object at rest will stay at rest, until acted on by an unbalanced force.

15. 14. Newton’s first law is sometimes known as the Law of _________________. • INERTIA

16. 15. What formula goes with Newton’s 2nd law? • F = m x a • Force = Mass x Acceleration • More mass means less acceleration unless you use MORE force!

17. 16. If you have a bulldozer and a Porsche at a stoplight, what would be the relationship between force, mass, and acceleration on these two vehicles? • The bulldozer has more mass so it needs more force to get it going or to make it stop. • The Porsche has less mass so it needs less force to get greater acceleration.

18. 17. What does Newton’s third law say? • For every action there is an equal and opposite reaction.

19. 18. This means that all forces act in _________________. • PAIRS

20. 19. List 5 action-reaction examples. • Hitting a baseball. • Swimming • Rocket taking off. • Rabbit hopping. • Cutting with scissors.