Quiz on Newton’s Laws

2. Quiz on Newton’s Laws

3. A person pushes a 48 kg sled of a frictionless surface with a constant force. The sled moves 382 m in 24.8 seconds. Assume that the sled starts from rest. • What is the acceleration? What is the final velocity? What is the weight of the sled? What is the force that the person supplied? List: m = 48 kg d = 382 m t = 24.8 s vi = 0 a = ? d = vit + ½ at2 382 = 0 + ½ a(24.82) a = 1.24 m/s2 for a? for v? v = vi + at v = 0 + 1.24(24.8) = 30.8 m/s

4. A person pushes a 48 kg sled of a frictionless surface with a constant force. The sled moves 382 m in 24.8 seconds. Assume that the sled starts from rest. • What is the acceleration? What is the final velocity? What is the weight of the sled? What is the force that the person supplied? List: m = 48 kg d = 382 m t = 24.8 s vi = 0 a = ? for Fg? Fg = mg Fg = 48(9.8) = 470.4 N for F? F = ma F = 48(1.24) = 59.5 N

5. 2. What is the acceleration if Ft = 638N and the coefficient of friction is 0.27. Ff Ft 54 kg F = ma Ft – Ff = ma 638 – 143 = 54a a = 9.2 m/s2 Ff = µmg Ff = .27(54)(9.8) Ff = 143 N

6. 3. a. What is the velocity at 30 s? ______ 4 m/s b. What is the acceleration at 30 s? _______ 0 40m c. How much distance was covered in 20 s? _______ d. How much distance was covered between 20s and 50 s? ______________ 120m

7. e. What is the acceleration during the last 10 s? ________ -0.4 m/s2 f. What is the acceleration during the first 20s? __________________ 0.2 m/s2

8. 4. N = ______ (m/s2) kg 5. Fg is ______________on earth. weight Weight 6. ______________ is due to a gravitational field. 7. The law of inertia states that balanced forces will result in _____________ acceleration. 0 8. Newton’s 2nd law states that acceleration is caused by _______and tempered by the ____________ of the object. force mass

9. 9. Newton’s 2nd law states that acceleration is _____________to the force and ______________________to the mass of the object. proportional inversely proportional 10. “Σ” means “_________” sum of 11. A __________________ is a push or a pull. force 12. When a person stand on the floor, the force that the floor pushes on the person is called the ______________ force. normal

10. 13. On earth, 1 kg weighs ______________. 9.8 N or 2.2 lbs. 14. _____________ is force(F) per area(A) Pressure 15. The unit for pressure is the ________________ Pascal 16. An object at rest remains at ________________ and an object in motion remains in _____________, unless acted on by ___________________________. rest motion force

11. 17. _______________ is another name for mass. inertia 18. When a person stand on the floor, the force that the person pushes on the floor is called the ______________ . weight

12. 19. What is the total distance covered? _____ 120 m 20. How much distance was covered in the first 20s? ______________ 40 m

14. Centrifugal Force Centrifugal Force points to the center of the circle.

15. Car Centripetal Force is the outward force that people feel when they are in a car going in a circle

16. Mass and inertia resist _____________in motion. change A Force is a push or a ________________ pull kg The official metric unit for mass is the _________ The official metric unit for force is the __________ N

17. Vector or Scalar V or S mass weight acceleration speed Force time distance velocity S V V S V V S V

18. Units Force time distance velocity N mass weight acceleration speed kg s N m/s2 m m/s m/s

19. When forces are balanced, they are in ___________ equilibrium weight Fg is called _____________ What is the formula for weight? Fg = mg weight ____________ is the force that a guy pushes on the floor. Balanced forces do not cause _____________ acceleration

20. What is the force in each rope? Plant 44 N 22N

21. Ft m = 3 kg a What is the weight of a 20 kg person? 196 N What is the acceleration if Sam pulls the rope with a force of 6 N? a = 2 m/s2

22. What is the pressure of a 400 N woman standing on one high heel? healprint: P = 4 000 000 Pa 1 cm on each side

23. What produces accelerations? Force What force is needed to keep a spaceship flying through frictionless space after it leaves earth orbit? Zero Zip Nada

24. If a deer hits the windshield of your car, how does the acceleration of the deer compare to the deceleration of the automobile? Poor deer, not so much for the car. How do forces occur: pairs triplets, etc? pairs

25. How does friction act against motion? Always in the direction opposite the velocity. How does the law of inertia apply to moving objects and stationary objects? An object in motion tends to stay in motion at the same velocity, and an object at rest tends to stay at rest.

26. What is the net force if 20 N and 30 N are acting in opposite directions? 10 N If a force of 200 N acts on an object and accelerates it at 5 m/s2, what is the mass of the object? F = ma m = F/a = 200/5 = 40 kg

27. When is an object in equilibrium? Balanced forces How do static and sliding friction compare? Static friction is slightly greater.

28. What would be the maximum possible resultant of 4 N and 5 N forces? 9 N What would be the minimum possible resultant of 4 N and 5 N forces? 1 N

29. What are Newton’s Three Laws of Motion? 1. An object at rest tends to stay at rest and an object in motion tends to stay in motion at the same velocity. 2. a = F/m 3. For every force there is an equal and opposite force.