AP PHYSICS 1 UNIT 3 PRACTICE TEST NAME FREE RESPONSE PROBLEMS Show your work for partial credit. Circle or box your answers. Include the correct units and the correct number of significant figures in your answers! 1. Two blocks are connected by a string of negligible mass that passes over massless pulleys that turn with negligible friction, as shown in the figure at right. The mass m 2 of block 2 is greater than the mass m_1 of block 1. The blocks are released from rest. (a) The dots below represent the two blocks. Draw free-body diagrams showing and labeling the forces (not components) exerted on each block. Draw the relative lengths of all vectors to reflect the relative magnitudes of all the forces. (b) Derive the magnitude of the acceleration of block 2. Express your answer in terms of m 1, m 2, and g.
Block 3 of mass m 3 is added to the system, as shown at right. There is no friction between block 3 and the table. (c) Indicate whether the magnitude of the acceleration of block 2 is now larger, smaller, or the same as in the original two-block system. Explain how you arrived at your answer.
2. A student wants to determine the coefficient of static friction between a long, flat wood board and a small wood block. (a) Describe an experiment for determining the coefficient of static friction between the wood board and the wood block. Assume equipment usually found in a school physics laboratory is available. Draw a diagram of the experimental setup of the board and block. In your diagram, indicate each quantity that would be measured and draw or state what equipment would be used to measure each quantity. Describe the overall procedure to be used, including any steps necessary to reduce experimental uncertainty. Give enough detail that another student could replicate the experiment. (b) Derive an equation for the coefficient of static friction in terms of quantities measured in the procedure from part (a).
A physics class consisting of six lab groups wants to test the hypothesis that the coefficient of static friction between the board and the block equals the coefficient of kinetic friction between the board and the block. Each group determines coefficients of kinetic and static friction between the board and the block. The groups results are shown at right, with the class averages indicated in the bottom row. (c) Based on these data, what conclusion should the students make about the hypothesis that the static and kinetic friction are equal? The static and kinetic coefficients are equal. The static and kinetic coefficients are not equal. Briefly justify your reasoning. (d) A metal disk is glued to the top of the wood block. The mass of the block-disk system is twice the mass of the original block. Does the coefficient of static friction between the bottom of the block and the board increase, decrease, or remain the same when the disk is added to the block? Increase Decrease Remain the Same Briefly state your reasoning.
3. A 0.30 kg ball is in a cup of negligible mass attached to a block of mass M that is on a table. A string passing over a light pulley connects the block to a 2.5 kg object, as shown at right. The system is released from rest, the block accelerates to the right, and after 0.95 m the block collides with a bumper near the end of the table. The ball continues to move and lands on the floor at a position 2.4m below and 1.8 m horizontally from where it leaves the cup. Assume all friction is negligible. (a) Calculate the speed of the ball just after the block hits the bumper and the ball leaves the cup. (b) Calculate the magnitude of the acceleration of the block as it moves across the table.
(c) Calculate the mass M of the block. (d) if the mass of the ball is increased, the horizontal distance it travels before hitting the floor will decrease. Explain why this will happen.