Question

NTSB-QRT19: STUDENT PUSHES TWO SLOWING BLOCKS-FORCE ON BLOCK A student pushes the two blocks to the right. Block A has more mass than block B There is friction between the blocks and the table. (i) For the situation where the blocks are slowing down, which of the following statements is true about the magnitude of the forces a) The force that block exerts on block is greater than the force that block exerts on block b) The force that block. exerts on block 8 is less than the force that block Bertson block c) The force that blockererts on block 8 is equal to the force that block exerts on block 4 d) We cannot compare the forces unless we know how fast the blocks are showing down (i) For the situation where the blocks are slowing down, which of the following statement is true about the set force? a) The net force on block points to the right and is also the net force on black b) The ne force on Block points to the left and is c l othe net force on black B c) The net force on black points to the right and is greater than the met force on block d) The net force on black 4 points to the left and is greater than the net force on block c) The net force on black points to the right and is less than the net force on block B 1) The net force on black points to the left and is less than the net force on Black B 3) None of these are correct (i) For the situation where the blocks are moving along at constant speed, which of the following statements is true about the magnitude of the forces? a) The force that block exerts on block B is greater than the force that block B exerts on block b) The force that block exerts on block B is less than the force that block B exerts on black c) The force that block. exerts on black is equal to the force that block certs en block d) We cannot compare the forces unless we know how fast the blocks are slowing down (iv) For the situation where the blocks are moving along at a constant speed, which of the following statements is true about the net force? a) The net force on black 4 points to the right and is wel to the net force on block b) The nel force on black points to the left and is equal to the net force on block c) The net force on block 4 points to the righer and is grewer than the net force on block 8 d) The not force on black points to the left and is greater than the net force on block e) The net force on black points to the righer and is less than the net force on block B 1) The nel force on black points to the left and is less than the force on black 8) None of these are correct. ns For 6-16-2010 nTSB-RT20: Ropes Pulling identical Boxes Rope Tension Shown below are boxes that are being pulled by ropes along frictionless surfaces, accelerating toward the left. All of the boxes are identical and the accelerations of the boxes an indicated in cach figure Smallest Rank (from largest to smallest) the magnitude of the tension in these ropes. Largest 2 OR, all of these ropes have the same tension OR. We cannot determine the ranking for the tensions Please explain your reasoning,

Answer 1

) For the situation where the blocks are slowing down, which of the folloning statements is true about the magnitude of the forces? e The force that block A exerts on block B is equal to the force that block B exerts on block A. This is due to newton's third law according to which every action has equal and opposite reaction. () For the situation where the blocks are slowing down, which of the following statements is true about the net force? d The net force on block A points to the left and is greater than the net force on block B. we know that, net force mass x acceleration Since both blocks move together, they have same acceleration. but their masses are different. greater the mass, greater will be the net force hence block A has greater net force Since block A is slowing down, the net force must be directed opposite to direction of motion (ii) For the situation where the blocks are moving along at a constant speed, which of the following statements is true about the magnitude of the forces? The force that block A exerts on block B is equal to the force that block B exerts on block A e) This is due to newton's third law according to which every action has equal and opposite reaction.

(iv) For the situation where the blocks are moving along at a constant speed, which of the following statements is true about the net force? None of these are correct E) Since the blocks move at constant speed, the acceleration is zero. hence the net force on each block is zero