Kinematics

 Block of Mass

 Whiteboard

 Circle the letters marking all those statements that are correct. Any number of statements may be correct, and therefore each one must be examined on its merits. Do not simply drop the question after you have found one correct statement. A block of mass m is being pulled along the floor by a force T inclinded at an angle q as shown in the diagram. The coefficent of friction between the block and the floor is denoted by m. The magnitude of the force is such that the block moves with uniform velocity.

Q1: The magnitude of the normal force exerted on the block by the force is given by:
 a) mg d) mg - T sin q b) mg - T cos q e) T sin q c) mg + T cos q f) None of the above

Q2: The magnitude of the frictional force exerted on the block by the force is given by:

 a) T cos q d) m(mg - T cos q) b) T sin q e) Zero c) mg f) None of the above

Q3: During a horizontal displacement: Dx of the block:

a) The work done by the force T is given by TDx.
b) The work done by the force T is given by (T sin q) Dx.
c) Some of the work done by the force T is stored as potential energy in the system while the rest is converted into thermal internal energy.
d) The work done by the force T is equal to the kenetic energy change of the block.
e) The change in potential energy of the block-earth system is mgDx.
f) None of the above.

 References

 Arons, A.B. (1997) Teaching Introductory Physics, Wiley: NY

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