Physics 1710 Unit 1—Review
Review Activity (neuron reconnection time):
In your notes (without consulting other pages)
write down Three kinematic equations for
uniform acceleration:
• v = vinitial + a t
• r = rinitial + vintitial t + ½ a t 2
• vx 2 = v x,initial 2+ 2 ax Δx
vy 2 = v y,initial 2+ 2 ay Δy
Physics 1710 Unit 1—Review
1′ Lecture
• Newton’s Laws of Motion are:
 Acceleration (or deceleration) occurs if and
only if there is a net external force.
 a = F/m [Note this is a vector eqn.]
 The force exerted by a first object on a
second is always equal and opposite the
the force exerted by the second on the
first. F12 = - F21
Physics 1710 Unit 1—Review
3rd Law in Action—Tug of War
#2
F21
?
It’s the Law!
F12 = - F21
#1
F12
Physics 1710 Unit 1—Review
Third Law of Motion:
If two objects interact,
the force of the 1st on the 2nd is equal and opposite
to the force of the 2nd acting on the 1st body.
F12 = - F21
F12
#2
#1
F21
Physics 1710 Unit 1—Review
2nd Law of Motion: Example
Broken Atwood Machine
Friction
- μ g (m2 +m1)
F = g (m2 – m1)
– μ g (m2 +m1),
if m2 > m1
a = F/(m2 +m1)
a = g(m2 – m1)/(m2 +m1)
-μg
a
a
g m1
g m2
Physics 1710 Unit 1—Review
Laws of Motion
1st Law:
An acceleration is caused by a net external
force.
Draw Free Body
diagram!
Physics 1710 Unit 1—Review
Laws of Motion
1st Law:
An acceleration is caused by a net external
force.
Draw Free Body
diagram!
½ D ρA v 2
- mg
Physics 1710 Unit 1—Review
Laws of Motion in Action:
Sledding on a Hill
Draw “free body diagram”
F = mg sin Θ
Ff = μN
N = mg cos Θ
mg
Θ
ΣF = ma = F – Ff = mg sin Θ – μ mg cos Θ
Physics 1710 Unit 1—Review
• What will make the biggest difference in winning a
sledding race?
1. The mass of the sledder.
2. The weight of the sled.
3. The friction of the sled skids or
runners.
4. The slope of the hill.
Physics 1710 — e-Quiz
I think that the use of the Response Card system
contributes to the quality of my instruction in this
course.
1.
2.
3.
4.
Strongly agree.
20%
Agree.
Disagree.
25%
Strongly
disagree
12%
43%
1
2
3
4
Physics 1710 Unit 1—Review
Summary:
• Newton’s Laws of Motion are:
(1) Acceleration (or deceleration) occurs if and only
if there is a net external force.
(2) a = F/m [Note this is a vector eqn.]
(3) The force exerted by a first object on a second is
always equal and opposite the the force exerted by
the second on the first. F12 = - F21
Physics 1710 Unit 1—Review
Summary (cont’d.) :
• Weight is the force of gravity equal to g times the
mass of the object.
• g =9.80 N/kg
• Ff = μ N
• Free body diagrams are sketches of all the forces
acting on a body.
Physics 1710 Unit 1—Review
Summary (cont’d.) :
• In a moving or accelerating Frame of Reference
• v ′ = v – vframe of reference
• a ′ = a – aframe of reference
• The Centripetal acceleration is
• a = - ω2 r
or |a| = v 2/ |r|, toward the center.
Physics 1710 Unit 1—Review
Summary (cont’d.) :
• v = vinitial + a
t
• r = rinitial + vintitial t + ½ a t 2
• vx 2 = v x,initial 2+ 2 ax Δx
vy 2 = v y,initial 2+ 2 ay Δy
• Mass density ρ = M/V