Chapter 5 concepts and problems review

1. Chapter 5 concepts and problems review

2. First question • What is Newton’s first law? • What is Newton’s second law? • What is Newton’s third law?

3. ….And then… • Define acceleration. • If an object is moving at constant velocity, what is its acceleration?

4. ….And then… • Jeremy Bordelon applies a force of 10 N to three objects with masses of 1 kg, 2 kg and 3 kg. • Which experiences the greatest acceleration? • Which experiences the least acceleration?

5. ….And then… • Acceleration is always in the _________ direction as the applied force. • Explain this in terms of the string and the spool demonstration we did in class.

6. ….And then… • What are the units of force? • What are the units of mass? • What are the units of acceleration? • What are the units of velocity?

7. ….And then… • What is friction? • Friction always acts in the ________ direction to the motion of an object. • A book is lying at rest on top of a table. Is there a force of friction acting on the book?

8. ….And then… • What is air resistance? • What is terminal velocity? • If an object is falling at terminal velocity, what is the sum of the forces on the object?

9. ….And then… • Why does a parachute reduce a skydiver’s terminal velocity? • Two skydivers of equal mass jump out of a plane at the same time. One has a parachute that is twice as large as the other. Which has a higher terminal velocity?

10. ….And then… • Define pressure. • What are the units of pressure in the SI system? • Stacy Zambrana applies a force of 100 N on an area of 0.5 square meters, then applies the same force on an area of 0.1 meters. In which case has he applied the larger pressure?

11. ….And then… • Supriya Patel is standing at the top of the leaning tower of Pisa. He drops a bag of hammers and a watermelon at the same time. Explain why they hit the ground at the same time even though their masses are different.

12. ….And then… • Remember the demonstration of dropping the book with the piece of paper on it and the paper didn’t float up as the book dropped? Yeah, that was awesome. Explain how that happened.

13. ….And then… • What does ‘directly proportional to’ mean? • What does ‘inversely proportional to’ mean?

14. ….And then… • A 20,000 kg rocket accelerates at 1 m/s2. what is the applied force on the rocket?

15. ….And then… • What is the difference between force and pressure? • Which produces more pressure on the ground, a Nick Mylius lying down or a Nick Mylius standing up?

16. ….And then… • What is the acceleration of a 2000 kg Cessna just before takeoff if the engine thrust is 500 N?

17. ….And then… • Ty McDonald pushes a 2 kg book with a force of 20 N across a horizontal frictionless table. What is the acceleration of the book? • What is the acceleration if there happens to be a 4 N frictional force?

18. ….And then… • What is the difference between ‘proportional to’ and ‘equal to’? • Is force equal to or proportional to mass times accleration? • Is air resistance equal to velocity or proportional to velocity?

19. ….And then… • If an object is not moving, can we say that there are no forces action on it? • Give an example to support your reasoning.

20. ….And then… • Leah Rogienski is pushing a large crate across the floor. Her applied force is 200 N and the crate moves at constant velocity. What is the frictional force on the crate? • Leah then pushes the same crate with the same force across a different floor and this time the crate is accelerating. What can we now say about the force of friction as compared to before?

21. ….And then… • Why does a sharp knife cut better than a dull knife? • A 3kg object sits on a table. The area of the bottom of the object is 0.2 m2. what pressure does it produce?

22. ….And then… • An object experiences an acceleration of 24.5 m/s2. How many g’s is that? • The occupant of a car can survive a crash if the deceleration is not greater than 30 g’s. Calculate the force on a 70 kg person decelerating at that rate.