Transcript Document

Chapter 4 Test Review
Displacement, velocity, acceleration and force
are vectors.
Vectors are represented by arrows, the length
being the magnitude, the direction as indicated
The unit of force is the Newton (N)
a newton is a kg(m/s2)
mass
acceleration
Force is a push or pull, such as pushing on a
wall, or gravity pulling you down (weight)
SF = ma
mass = 10 kg
What is the force of gravity pulling down on this
ball? (10 extra credit points to whoever shouts out
the correct answer first…)
What is the net force if there is 10 N of air
resistance opposing the fall (10 points to
somebody else…)
Newton’s Third Law of Motion
For every action force, there is an equal
and opposite reaction force…
10 N
10 N
If there is no acceleration (constant
velocity), there is no net force. Forces
left = forces right. Forces up = forces
down.
80 m/s
A baseball player hits a baseball. What forces
are acting on the baseball, after the hit?
a. friction ?
(we’ll ignore air
resistance)
b. the force of the hit ?
c. the normal ?
d. gravity ?
e. tension ?
Friction is f = mN
100 Kg
pulled with a force of 10 N
at a constant speed of 5 m/s
What if the force of friction?
What is the normal force?
What is the coefficient of friction?
Label all of the forces
Fp (T)
N
Fpy
f
Fpx
mg
Box sliding down an inclined plane…
label the forces
N
f
F┴
mg
FII
Which force
pushes the box
down the
slope?
Label the forces…
Fp (T)
Fpy
N
Fpx
f
mg
F┴
FII
T1 = 30 N
q1 = 85°
T2
T3 = 50 N
q3 = 42°
A ball with a mass of 20 Kg
hangs from three ropes. What
is the tension in the middle
rope?
mg = 20 Kg (9.81 m/s2) = 196.2 N
sin 85° (30N) + sin 42° (50N) + T2 = 196.2N
T2 = 196.2N - sin 85° (30N) - sin 42° (50N)
T2 = 132.8N