1. Which of the following unit expressions does not have the dimensions of speed?
   • (A) m/s
   • (B) km/h
   • (C) cm/min
   • (D) mm/s²
   • (E) ft/day

2. An object is moving in the positive direction and its speed is decreasing.
   • (A) The object's velocity is positive and its acceleration is 0.
   • (B) The object's velocity is positive and its acceleration is negative.
   • (C) The object's velocity is positive and its acceleration is positive.
   • (D) The object's velocity is negative and its acceleration is positive.
   • (E) The object's velocity is negative and its acceleration is negative.

3. The driver of a sports car and the driver of a Jeep meet on a back road and decide to have a race. Both vehicles reach the finish point at exactly the same time, the Jeep having gone cross-country, the sports car having followed the road.

   (A) The average velocity of the sports car was greater than that of the Jeep. (B) The average velocities of the two vehicles were the same. (C) The average speeds of the two vehicles were the same. (D) The average speed of the Jeep was greater than that of the sports car. (E) The average speed of the sports car was the same as the magnitude of its average velocity.

4. A ball is thrown vertically upward. Neglect any effects due to air resistance. Consider the acceleration of the ball after it is released.
   • (A) The acceleration has a constant magnitude of g and is directed downward.
   • (B) The acceleration at the top of the trajectory is 0.
   • (C) The acceleration is directed downward when the ball is moving upward, and is directed upward when the ball is moving downward.
   • (D) The acceleration is directed upward throughout the ball's motion.
   • (E) The acceleration is 0 throughout the ball's motion.

5. Consider the resultant of the addition of three vectors, each of magnitude of 1 unit. The magnitude of the resultant:
   • (A) is 0
   • (B) is 3 units
   • (C) cannot be less than 1 unit
   • (D) cannot be more than 2 units
   • (E) will be between 0 and 3 units, depending on the directions of the vectors being added

6. A pellet gun is aimed directly at an apple hanging in a tree. (i.e. A straight line drawn along the axis of the gun barrel and extended to the tree would pass through the apple.) The gun is fired, and at the instant the pellet leaves the barrel of the gun the apple stem breaks and the apple falls. Ignoring any effects due to air resistance:
   • (A) The pellet misses the apple, passing directly through the apple's original location in the tree;
   • (B) The pellet hits the apple;
   • (C) The pellet misses the apple, passing below the apple as it is falling;
   • (D) The pellet may or may not hit the apple, depending on the original height of the apple;
   • (E) The pellet may or may not hit the apple, depending on the masses of the pellet and apple.

7. A box of weight W remains at rest on the floor when you push it with a force F. The magnitude of the net force acting on the box is:
   • (A) 0
   • (B) W
   • (C) F
   • (D) F - W
   • (E) F + W

8. An object is falling through the air at constant velocity (air resistance is present). Which of the following statements is true?
   • (A) The net force on the object is downward and is proportional to its mass.
   • (B) The net force on the object is downward and is independent of its mass.
   • (C) The net force on the object is zero.
   • (D) The net force on the object is upward and is proportional to its mass.
   • (E) The net force on the object is upward and is independent of its mass.

9. Three non-collinear forces, F1, F2, and F3 are acting on an object. The resulting acceleration of the object is
   • (A) in the direction of the smallest of F1, F2, and F3.
   • (B) in the direction of the largest of F1, F2, and F3.
   • (C) in the direction of the vector sum F1 + F2 + F3.
   • (D) in the direction of F1 - F2 - F3.
   • (E) in the direction of F1 + F2 - F3.

10. Two astronauts, 1 and 2, of masses m₁ and m₂ respectively, are initially at rest outside their spacecraft. Astronaut 1, of mass m₁, pushes astronaut 2 with a force F. The force on astronaut 1 due to astronaut 2 is:
    

ANSWERS:

1. (D) - speed has dimensions of [L]/[T].
2. (B) - velocity is in direction of motion, and decreasing speed means the acceleration is oppositely directed to the velocity.
3. (B) - Although the vehicles cover different distances, their displacements are the same, and occur in the same amount of time.
4. (A) - Force of gravity does not change, so acceleration due to gravity is constant throughout motion.
5. (E)
6. (B) - recall 'shoot the duck' demo in class. Both the pellet and the apple have the same vertical acceleration due to gravity, so if the pellet would have hit the apple without gravity being present, it will hit the apple when gravity is present.
7. (A) - Net force on an object at rest is 0 (Newton I).
8. (C) - Constant velocity means acceleration is 0 and so net force is 0 (Newton I).
9. (C) - vector nature of Newton II.
10. (B) - Newton III

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