Revision sheet
Vocabulary to study from the book (all yellow highlighted words):
Force
System
Contact force
Field force
Agents
Free body diagram
Force net
Newton’s second law
Newton’s first law
Inertia
Equilibrium
Weight
Gravitational field
Apparent weight
Weightlessness
Drag force
Tension force
Terminal velocity
Important equations:
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Newton’s second law  F=mass x acceleration
Total forces on an object in a system: Fnet=F1+F2 (if in the same direction)
Total forces on an object in a system: Fnet=F1-F2 (if in opposite direction)
Weight of the object: Fg= mass x Gravity (9.8)
Steps of free body diagram:
Steps to solve any free body problem:
Practice problems:
1) A skydiver falls downward through the air at constant velocity. (The air exerts an
upward force on the person.)
2) Two horizontal forces, 225 N and 165 N, are exerted on a canoe. If these forces are
applied in the same direction, find the net horizontal force on the canoe.
3) If the same two forces as in the previous problem are exerted on the canoe in
opposite directions, what is the net horizontal force on the canoe? Be sure to
indicate the direction of the net force.
4) Draw a free-body diagram of a bag of sugar being lifted by your hand at an
increasing speed. Specifically identify the system. Use subscripts to label all forces
with their agents. Remember to make the arrows the correct lengths.
5) You place a 22.50-kg television on a spring scale. If the scale reads 235.2 N, what
is the gravitational field?
6) You are riding in an elevator holding a spring scale with a 1-kg mass suspended
from it. You look at the scale and see that it reads 9.3 N. What does this tell you
about the elevator’s motion?