Download Worksheet 7 - Forces and Free Body Diagrams

Worksheet #7 Newton’s
Laws and Free Body
Diagrams
Supplemental Instruction
Iowa State University
Leader: Wesley
Course: PHYS 221
Instructor: Whisnant
Date: 02/04/2014
1. (Newton’s Laws) The two blocks shown below are connected by a heavy rope with a
mass of mR. An upward force F is applied as shown.
a. Draw a free body diagram for all three components of apparatus, and indicate
what body exerts each force
b. What is the acceleration of the entire system?
c. What is the tension at the top of the heavy rope?
d. What is the tension at the midpoint of the rope?
MR = 4.00 kg
M = 6.00 kg
m = 5.00 kg
F = 200 N
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Do NOT plug in numbers until you have solved for the desired variable!
Try to solve each problem algebraically first.
2. What net force is required for a car of mass m traveling at a velocity of v to literally stop
on a dime? (The diameter of a dime is equal to d.)
m = 850 kg
v = 45.0 km/h
d = 1.8 cm
3. Two crates, one with mass m1 and the other with mass m2 sit on a frozen pond, connected
by a massless rope. A woman pulls horizontally on crate with m1 with a force F
(unknown) that gives the crate an acceleration of a.
a. What is the acceleration of crate with m2?
b. Draw a free body diagram for crate 2.
c. Draw a free body diagram for crate 1, and find the direction of the net force on
crate 1.
d. Calculate the magnitude of F.
m1 = 6.00 kg
m2 = 4.00 kg
a = 2.50 m/s2