Midterm exam Review

1. Midterm exam Review

2. When an object is in free fall…. • a. It always has an acceleration of 10 m/s2 downward • b. It is travelling a greater distance each successive second • c.Its velocity is changing by -10 m/s every second • d. It is not under the influence of anything except gravity • e. all of the above.

3. ____A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car’s average acceleration? • a. 0.17 m/s2 b. 1.67 m/s2 c. 6 m/s2 • d. 7 m/s2 e. none of these

4. A ball is thrown upwards with a velocity of 40 m/s and caught when it comes back down. If there is no air resistance, the velocity of the ball at its highest point would be • a. 10 m/s b. 10 m/s2 c. 0 m/s d. 40 m/s e. -10 m/s

5. If a skydiver jumps out of a plane he will eventually stop accelerating (before the parachute is opened), This happens because…. • a. He keeps the same speed as he jumped out of the plane with the entire time he’s falling • b. The skydiver will keep on accelerating until the parachute is opened or he hits the ground • c. The air resistance will eventually become so strong that gravity no longer accelerates him, and he reaches terminal velocity • d. Because terminal velocity is reached once the skydiver is travelling at the speed of sound

6. ___Suppose a jumper claims a hang time of 2 seconds when jumping straight up. Then that jumper must be able to leave the ground with a speed of • a. 10 m/s. • b. 5 m/s. • c. 1 m/s. • d. 30 m/s. • e. 20 m/s.

7. Suppose a small plane can fly at 170 km/h relative to the surrounding air. Suppose also that there is a 60 km/h headwind (a wind blowing in the opposite direction as the plane is flying). How fast does an observer on the ground see the plane go? • a.110 km/h • b. 230 km/h • c. 60 km/h • d. 170 km/h • e. 5 km/h

8. A 10 kg object is accelerated from rest to a speed of 4 m/s, how much work was done on the object? • a. 80 J • b. 40 J • c. 2.5 J • d. 400 J

9. What is the equation for Momentum?

10. According to Newton’s 2nd Law What is the relationship between mass and acceleration?

11. ____ A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always • a. in the direction of motion. • b. directed upward. • c. opposite its velocity. • d. directed downward.

12. ____The reason padded dashboards are used in cars is that they • a.increase the force of impact in a collision. • b.decrease the momentum of a collision. • c.increase the time of impact in a collision. • d.look nice and feel good. • e.decrease the impulse in a collision.

13. ____ Superman and a very massive asteroid are both at rest in space, if superman throws the asteroid, which of the two objects will most faster, Superman or the asteroid? • a. They both move at the same speed. • b. The asteroid • c. Superman

14. A 4.0-kg ball has a momentum of 20.0 kg·m/s. What is the ball's speed? • a. 80.0 m/s • b. 5.0 m/s • c. 0.2 m/s • d. 20.0 m/s • e. none of the above

15. The change in momentum of an object is equal to the • a. velocity change of the object. • b. object's mass times the force acting on it. • c. force acting on it times its velocity. • d. force acting on it. • e. impulse acting on it.

16. ____ Compared to a sports car moving at 30 miles per hour, the same sports car moving at 60 miles per hour has • a. four times as much momentum. • b. twice as much momentum. • c. the same momentum.

17. 2 m/s 1 kg 1 kg • If a 1 kg glider moving at 2 m/s collides inelastically with another glider of the same mass that was initially at rest • ____ 22. What was the initial momentum of the entire system (both carts) • a. 2 kg m/s b. 4 kg m/s c. 3 kg m/s d. 0 kg m/s • ____ 23. What is the final momentum of the entire system (both carts)? • a. 2 kg m/s b. 4 kg m/s c. 3 kg m/s d. 0 kg m/s • ____ 24. What is the velocity of the two combined carts after the collision? • a. 0 m/s b. 1 m/s c. 1.5 m/s d. 2 m/s

18. True/False • Indicate whether the sentence or statement is true or false. • ____ 27. Impulse is defined as the force exerted on an object times the time it lasts. • ____ 28. When a baseball player follows through in hitting the ball, the contact time with the ball is longer. • ____ 29. When two objects collide and stick together, the collision is said to be inelastic. • ____ 30. If a net force acts on a system, the system's momentum will change. • _____ 33. Impulse is equal to the change in momentum

19. The mass of a sheep that weighs 110 N is about • a. 1100 kg. • b. 11 kg. • c. 110 kg. • d. 1 kg. • e. none of the above

20. The center of gravity of a human body is located at a point • a. that can change depending on how the body is oriented. • b. that is always directly behind the belly button, no matter how the body is oriented • c. that is fixed no matter what. • d. none of the above

21. ___Earth pulls on the moon, and similarly the moon pulls on Earth. This is evidence that the • a. Earth's and moon's pulls comprise an action-reaction pair. • b.Earth and moon are simply pulling on each other. • c.both a and b • d.neither a or b

22. Two gliders having the same mass and the same speed move toward each other on an air track and stick together. After the collision, the velocity of the gliders is • a. There is not enough information to say. • b. the same as the original velocity. • c. zero. • d. one half the original velocity. • e. twice the original velocity.

23. ____ 28. A ball is thrown directly upward at a speed of 30 m/s, how long will it take to reach its highest point? • A ball is thrown directly upward at a speed of 30 m/s, how long will it take to reach its highest point? • a. 1 sec • c. 4 sec • b. 3 sec • d. 6 sec

24. An object thrown into the air with a spin rotates about its • a. geometric center. • b. center of gravity. • c. edge. • d. none of the above • e. midpoint.

25. In an elevator that is accelerating in the downward direction, you will feel as if you weigh ______ but in actuality you will weigh ____________. • a. Less, more • b. More, less • c. The same, more d. less, the same

26. ____ 11. When you release the open end of a balloon the balloon will fly across the room, which of Newton’s Laws best explains this? • a. • 1st Law b. 2nd Law c. 3rd Law

27. A 5-N force and a 30-N force act in the same direction on a 7 kg object. What is the acceleration of the object? • a.35 m/s2 • b. 5 m/s2 • c. 7 m/s2 • d. 3.57 m/s2

28. A tennis ball and a bowling ball are dropped at the same time. Which ball has the greater gravitational force acting on it? • a. The bowling ball • b. The tennis ball • c. They both have the same force acting on them.

29. Once a satellite is put into orbit in outer space it will stay in orbit forever moving at a constant speed without engines ever firing, which of Newton’s Laws accounts for this? • a. 1st Law b. 2nd Law c. 3rd Law

30. ____ True/False • Indicate whether the sentence or statement is true or false. • ____ 33. Friction refers to the force between two surfaces that are sliding past each other. • ____ 34. If a hockey puck were to slide on a perfectly frictionless surface, it will eventually slow down because of its inertia. • ____ 35. The acceleration of an object is inversely proportional to the net force acting on it. • ____ 36. How heavy you ‘feel’ depends on the normal force acting on you, not your actual weight. • ____ 37. If you were riding in a car that was moving at a constant velocity and threw a baseball straight up, it would land in the back of the car. • ____ 38. The force due to gravity acting on an object is also referred to as its mass. • ____ 39. Whenever one object exerts a force on another object, the second object always exerts a force back on the first object.

31. If a rider in a car does not have her seatbelt on and the car get into a head on collision the rider will likely be thrown forward through the windshield, this is an example of Newton’s _____ Law. • 1st b. 2nd c. 3rd d. 4th

32. ____ A vector is a quantity that has • a. magnitude and time b. time and direction c. magnitude and direction

33. _____5. The horizontal component of a projectile's velocity is never affected by • a. a horizontal wind • b. gravity • c. the vertical component of its velocity. d. b & c

34. In the absence of air resistance, the angle at which a thrown ball will go the farthest is • a. 15⁰ b. 30⁰ c. 45⁰ d. 60⁰ e. 75⁰

35. A baseball is hurled into the air at an angle of 30 degrees above the horizontal and lands on a target that is at the same level as that where the baseball started. The baseball will also land on the target if it is thrown at an angle of • a. 20⁰ b. 40⁰ c. 50⁰ d. 60⁰ e. none of the above

36. Suppose a small plane can fly at 170 km/h in the North direction. Suppose also that there is a 60 km/h Northern wind. What is the plane’s resultant velocity? • 5 km/h b. 60 km/h c. 110 km/h d.170 km/h e. 230 km/h

37. What is the resultant of the two vectors 75 km East & 25 km West? • 100 km East b. 100 km West c. 50 km East d. 50 km West e.25 km West

38. City B is directly East of City A. If a plane wishes to travel from City A to City B while there is a strong wind that is directed North, in which direction should the plane direct itself so that it winds up in City B? A B

39. A projectile is launched upward at some angle. If it takes 6 seconds to reach its highest point, what was its initial vertical velocity?

40. A bomber plane, flying at a high speed, is planning to drop a bomb onto a city, in order to hit the city when should the bomber release the bomb. • a. Before it reaches the city • b. after it passes the city • c. when its directly above the city

41. True/False Indicate whether the sentence or statement is true or false. • ____ 22. Mass is a vector quantity. • ____ 23. A single vector can be replaced by two vectors in the x- and y-directions that are at right angles to each other. • ____ 24. If a ball is thrown at an angle of 70 degrees, it’s x-component of velocity is larger than its y-component of velocity. • ____ 25. Speed is a vector quantity. • ____ 26. An object thrown at an angle of 20˚ will have a longer hang-time than an object thrown at 60˚.

42. A brick has a weight of 10 N, if this brick is at rest in your hands what is the net force on it?

43. A projectile launched with a speed of 30 m/s at an angle of 70° will… • a. will initially be moving faster horizontally than it is vertically • b. will initially be moving faster vertically than it is horizontally • c. will initially be moving equally as fast horizontally as it is vertically • d. all of the above 70°

44. If you swing a baseball bat, which part of the bat has the fastest linear speed.. • A) the end of the bat • B) the handle of the bat • C) the middle of the bat • D) all parts of the bat have the same linear speed

45. If you swing a baseball bat, which part of the bat has the fastest rotational speed.. • A) the end of the bat • B) the handle of the bat • C) the middle of the bat • D) all parts of the bat have the same linear speed

46. **Not on 2013 TEST**If the dot on the below picture represents the Center of Gravity of the block, will it topple or stay upright?

47. When you punch a wall, which of the following values are larger compared to when you punch a pillow? • A) change in momentum • B) Impulse • C) Change in speed • D) Force • E) all of the above

48. A car goes from being at rest to a speed of 30 m/s in 6 seconds, what is the cars acceleration?

49. Which is more “elastic”, a tennis ball or a billiard ball?

50. A calorie is a unit for what type of quantity?