Unit 3.9 Study Guide (Intro)

1. A book rests motionless on a table. Which forces act on the book?​ A) Gravity only​ B) Gravity and the table’s normal force​ C) Gravity and friction​ D) Normal force only 2. A ball is thrown straight upward. At the very top of its path, what forces act on it?​ A) Only gravity​ B) Gravity and air resistance upward​ C) Gravity and air resistance downward​ D) No forces act on it 3. A car moving at a constant velocity has:​ A) A net force acting forward​ B) A net force acting backward​ C) No net force​ D) Increasing acceleration 4. A 5 kg box is pushed across a rough surface at constant speed. What can you say about the forces?​ A) Applied force > frictional force​ B) Applied force < frictional force​ C) Applied force = frictional force​ D) Friction force = 0 5. When drawing a free body diagram, you should include:​ A) All forces acting on the object​ B) Only the largest force​ C) Forces the object exerts on others​ D) The direction the object moves, but not the forces 6. A ball falling straight down has what forces acting on it (ignoring air resistance)?​ A) Only gravity​ B) Gravity and normal force​ C) Gravity and friction​ D) Gravity and tension 7. Which of the following best states Newton’s 1st Law?​ A) An object stays at rest unless friction acts on it​ B) An object stays at rest or moves at constant velocity unless acted on by an outside force​ C) A net force is needed to keep an object moving​ D) An object always accelerates in the direction of gravity 8. A balloon flies around the room when the air rushes out of its open end. Which law explains this?​ A) Newton’s 1st Law​ B) Newton’s 2nd Law​ C) Newton’s 3rd Law​ D) Law of Inertia 9. According to Newton’s 3rd Law, when you push a wall with 50 N of force, the wall:​ A) Pushes back on you with less than 50 N​ B) Pushes back on you with 50 N​ C) Pushes back with more than 50 N​ D) Does not push back 10. If the same force is applied to two objects, one with more mass, which accelerates more?​ A) The heavier object​ B) The lighter object​ C) Both equally​ D) Neither 11. A car suddenly stops and a passenger lurches forward. Which law is demonstrated?​ A) 1st Law​ B) 2nd Law​ C) 3rd Law​ D) Conservation of momentum 12. A 500 kg car is driving down the road with a constant velocity of 20 m/s. What is the net force acting on the car?​ A) 10,000N​ B) 25 N​ C) 0.04 N​ D) 0 N 13. A 10 kg object is pushed with a 60 N force east and a 30 N force west.​ Find the net force and acceleration.​ A) 30 N east, 3 m/s²​ B) 30 N west, 3 m/s²​ C) 90 N east, 9 m/s²​ D) 6 N east, 0.6 m/s² 14. A 1,200 kg car accelerates at 2 m/s² east while a 600 N frictional force acts west.​ What is the total applied force?​ A) 600 N​ B) 2,400 N​ C) 3,000 N​ D) 3,600 N 15. A 5 kg box experiences 20 N right and 15 N upward. What is the magnitude of the net force?​ A) 5 N​ B) 25 N​ C) 20 N​ D) 35 N 16. A 60 kg skydiver is falling through the air. The force of air resistance is equal to 288N. What is the acceleration of the sky diver?​ A) 4.8 m/s²​ B) 5.0 m/s²​ C) 60 N​ D) 300 N 17. A box is pulled north with 40 N and east with 30 N. Find the net force magnitude.​ A) 50 N​ B) 10 N​ C) 35 N​ D) 70 N 18. A 12 kg object moves at constant velocity while a 36 N force acts on it.​ What must the frictional force be?​ A) 0 N​ B) 12 N​ C) 24 N​ D) 36 N 19. The force of friction always acts:​ A) In the same direction as motion​ B) Opposite to motion​ C) Perpendicular to the surface​ D) Straight downward 20. Static friction:​ A) Only acts on moving objects​ B) Keeps objects at rest until a threshold is exceeded​ C) Is weaker than kinetic friction​ D) Is constant no matter what 21. Kinetic friction is:​ A) The friction acting on moving objects​ B) Always greater than static friction​ C) Always zero​ D) The same for all surfaces 22. A 15 N force tries to push a box, but maximum static friction is 18 N. What happens?​ A) The box accelerates​ B) The box moves at constant speed​ C) The box does not move​ D) The box moves but slows down 23. A 20 N box is sliding on a surface with μk=0.4. Find the frictional force.​ A) 4 N​ B) 8 N​ C) 12 N​ D) 20 N 24. If you push a box harder and harder, what happens to the static frictional force before it starts moving?​ A) It stays constant​ B) It increases to match your push until a maximum value​ C) It decreases​ D) It becomes zero 25. Hooke’s Law is written as:​ A) F=ma​ B) F=kx​ C) F=mg​ D) F=μFn​ 26. A spring with k=200 N/m is stretched 0.25 m. What is the force?​ A) 25 N​ B) 50 N​ C) 100 N​ D) 200 N 27. A spring with k=150 N/m stretches by 0.10 m. What is the force?​ A) 1.5 N​ B) 15 N​ C) 150 N​ D) 1,500 N 28. A 3 kg mass hangs from a spring with k=120 N/m.​ Will the spring stretch more than 0.25 m?​ A) Yes, because Fg=29.4 and x=0.245​ B) No, it will stay exactly 0.25 m​ C) No, it will compress​ D) Cannot be determined 29. A spring stretches 0.08 m when a 4 N force is applied. What is its spring constant?​ A) 5 N/m​ B) 40 N/m​ C) 50 N/m​ D) 80 N/m 30. If two springs are stretched the same distance where one has a a k=0.5 and the other has a k=2, how will the forces differ between the two springs?​ A) Spring A exerts the greater force because it is easier to stretch​ B) Spring B exerts the greater force because it has a larger spring constant.​ C) Both springs exert the same force because they are stretched the same distance.​ D) Spring A exerts four times the force of Spring B because 2/0.5 = 4