Question 19 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? Select two answers. 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. 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 C ol o SR beginning of the time interval and at the end of the time interval. Use a mass balance to measure the mass of the block. 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. Question 20 Experiment Number Mass of Object (kg) Magnitude of Net Force (N) Time that Force Is Applied (s) Initial Velocity (m/s) Final Velocity (m/s) 1 2 4.0 3 0 6 2 2 4.0 3 3 =3 3 2 4.0 3 -3 -9 An object is used in three different experiments so that a student can analyze the motion of the object when a net force is exerted on it. The data obtained from the three experiments are shown in the table. How can the student use the data to determine the relationship between the object's change in momentum and the direction of the net force exerted on the object? Observe that the magnitude of the net force and the amount of time that the force is applied remain the same in each experiment. Therefore, the net force changes the momentum of the object in the same direction for all experiments. Observe that the magnitude of the net force, the amount of time that the force is applied, and the mass of the object remain the same in each experiment. Therefore, the net force changes the momentum of the object in the same direction for all experiments. Observe the direction of the velocity vectors for the initial and final velocity measurements for each experiment. If the final velocity is negative, the net force changes the momentum in the opposite direction of motion. If the final velocity is positive, the net force changes the momentum in the same direction of motion. The student can calculate the change in the velocity of the object for each experiment. If the object decreases its speed or changes direction, the net force changes the momentum in the opposite direction of motion. If the object increases its speed and travels in the same direction, the net force changes the momentum in the same direction of motion. Question 21 An object of mass 5 kg travels in the positive direction with a speed of 1 2. The object collides with a second object that exerts an average net force over an interval of time such that the 5 kg object comes to rest. Which of the following best predicts the change in momentum for the 5 kg object? @ The change in momentum is in the negative direction. @ The change in momentum is in the positive direction. The change in momentum is zero. The direction of the change in momentum cannot be determined without knowing the value of the average force and time in which the force is exerted