AP Physics 1 Question 131: Answer and Explanation

Test Information

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Question: 131

1. It is known that a lab cart is moving east at 25 cm/s at time t1 = 0.10 s, and then moving east at 15 cm/s at t2 = 0.20 s. Is this enough information to determine the direction of the net force acting on the cart between t1 and t2?

  • A. Yes, since we know the cart is slowing down, its momentum change is opposite the direction of movement, and the net force is in the direction of momentum change.
  • B. No, because we don’t know whether forces such as friction or air resistance might be acting on the cart.
  • C. No, because we don’t know the mass of the cart.
  • D. Yes, since we know the cart keeps moving to the east, the net force must be in the direction of motion.

Correct Answer: A

Explanation:

A-Net force includes the contributions of all forces, including friction or air resistance; and net force is in the direction of acceleration, not of motion.