Question

A student must conduct an experiment in which a block is pulled across a horizontal surface by a spring scale so that a nonzero change in momentum of the block can be determined for a specific time interval. The student also has access to measuring tools that are found in a typical physics laboratory. Which of the following experiments could the student conduct to determine the change in momentum of the cart?
a. Attach the spring scale to the block, and pull the block at a constant speed as it travels across the horizontal surface. Record the force that the spring scale exerts on the block. Use a stopwatch to determine the time that the block is in motion.
b. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Record the force that the spring scale exerts on the block. Use a stopwatch to determine the time that the block is in motion.
c. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval.
d. Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval. Use a meterstick to measure the distance traveled by the block in the given time interval

Answer 1

Complete option C is;

Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval. Use a mass balance to measure the mass of the block

Answer:

B: Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Record the force that the spring scale exerts on the block. Use a stopwatch to determine the time that the block is in motion.

C: Attach the spring scale to the block, and pull the block so that its speed increases as it travels across the horizontal surface. Use the motion detector to record the speed of the block at the beginning of the time interval and at the end of the time interval. Use a mass balance to measure the mass of the block

Explanation:

We know that formula for change in momentum is;

Ft = m(v - u)

Where left hand side is impulse and right hand side is change in momentum.

Now, looking at the options, the most accurate will be options B and C because they depict the accurate parameters needed to calculate change in momentum unlike option A and D that deal with constant speed and & distance respectively which we don't need to calculate change in momentum.