Supplementary Syllabus for Physics 1105-304 s1

PHYSICS 1403, QUIZ 2 Chapter 4, July 19, 2004 Partial credit will be LIBERAL, provided that you show your work! USE BACK IF NECESSARY! (Please tell me you have done so!)

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1. (10 points) Newton’s Laws a. Using complete, grammatically correct English sentences, state Newton’s 1st Law of Motion.

b. Using complete, grammatically correct English sentences, state Newton’s 3rd Law of Motion.

2. (20 points) A box, mass m = 15 kg, is resting on a flat table. A person attaches a FP = 100 N rope to it and pulls it upward with a force FP = 100 N, as in the first figure. The box does not move. The free body diagram is shown in the first figure.  a. Write an equation which results by applying Newton’s 2nd Law to this problem in the vertical (y) direction. Writing it in symbols, without substituting in numbers, will receive more credit than writing it with numbers substituted in! (Hint: What is the acceleration in the vertical direction?)

b. Use the equation of part a to compute (find a numerical value for) the normal force FN on the box due to the table. (Hint: Is the normal force equal and opposite to the weight?)

For parts c and d, the person increases the upward force on the rope to FP = 200 N, as shown in the second figure. Since FP > mg (the box’s weight) the box is lifted off of the table. The normal force becomes zero and the box accelerates upward. The free FP = 200 N body diagram for this case is shown in the second figure.      c. Write an equation which results by applying Newton’s 2nd Law to this problem in the vertical (y) direction. Writing it in symbols, without substituting in numbers, will receive more credit than writing it with numbers substituted in!

d. Use the equation of part c to compute (find a numerical value for) the acceleration a of the box.