PHYSICS 1306, QUIZ 3
Chapter 4
February 19, 2003
Partial credit will be LIBERAL, provided that you show your work!
USE BACK IF NECESSARY! (Please tell me you have done so!)
Name: ______________________
1.
(10 points) Newton’s Laws
a. Using complete, grammatically correct English sentences, state Newton’s 1st Law of Motion.
b.
2.
Social Security Number ______________________
Using complete, grammatically correct English sentences, state Newton’s 3rd Law of Motion.
(20 points)
A box of mass m = 20 kg is resting on a flat, frictionless table. For parts a and b, a
person pushes vertically downward on the box with a force FP = 50 N, as is shown in
the first figure. The free body diagram in this case 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 terms of 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 on the box due
to the table. (Hint: Is the normal force equal and opposite to the weight?)
For parts c and d, a person attaches a rope to the same box and pulls it upward with a
force FP = 220 N, as is shown in the second figure. Since FP > mg (the box’s weight)
the box is lifted upward off of the table. The normal force thus becomes zero and the box
accelerates upward. The free body diagram 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 terms of 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 of the box.