1. Suppose that a car traveling to the west (-X direction) begins to slow down a
ID: 2306064 • Letter: 1
Question
1. Suppose that a car traveling to the west (-X direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct? A) Its acceleration is positive. B) Its acceleration is negative. C) Its acceleration is zero. D) Its acceleration is decreasing in magnitude as the car slows down. Answer: 2. A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, and then 1.0 km north to return to its starting point. This trip takes 45 min. What was the bear's average velocity? A) 0.00 km/h B) 0.067 km/h C) 4.0 km/h D) 5.3 km/h Answer: 3. When a ball is thrown straight up with no air resistance, the acceleration at its highest point A) is upward B) is downward C) is zero D) reverses from upward to downward E) reverses from downward to upward Answer: 4. A 20-ton truck collides with a 1500-lb car. Which of the following statements must be true? A) During the collision, the force on the truck is greater than the force on the car. B) During the collision, the force on the truck is equal to the force on the car. C) During the collision, the force on the truck is smaller than the force on the car. D) The truck did not slow down during the collision, but the car did. E) The car did not slow down during the collision, but the truck did. Answer: 5. A person who normally weighs 700 N is riding in a rather swift elevator that is moving at a constant speed of 9.8 m/s. If this person is standing on a bathroom scale inside the elevator, what would the scale read? A) more than 700 N B) less than 700 N C) 700 N D) It could be more or less than 700 N, depending on whether the elevator is going up or down. Answer:Explanation / Answer
1. The car is slowing down while moving along the -x axis. So the acceleration is positive.
2. Total displacement is zero. So the average velocity is zero.
3. The acceleration at the highest point is downward due to gravity.
4. The force on the truck is equal to the force on the car, due to Newton's 3rd law.
5. Option d. The weight would depend on the direction of acceleration.
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