10-05- 11
Agenda
HOMEWORK CHECK
Place on your desk:
*Calculator
*Orange homework chart
*Newton’s 1st Law Worksheet
 1) What is the weight of a 12 Kg stone?
120 N
 2) Calculate in Newtons the weight of a
1.5 Kg melon. What is weight in
pounds? [1Kg=2.2 lbs]
FW=(m*g)=(1.5Kg)(9.8m/s2)
=14.7 N* (1Kg/9.8N)(2.2 lb/1Kg)
1) Warm-Up
5 min
2) Coupons!
3) Vocab. Words 10 min
4) Newton’s 2nd Law 15 min
5) Board Notes for 2nd law 10 min
6) Newton’s 2nd Law Worksheet
30 min
7) Balloon Rocket mini-lab 15 min
Vocab.
1. Law of Inertia: every object (body) continues in a state
of rest, or motion in straight line at constant speed,
unless it is compelled to change by forces exerted upon
it.
2. Mass: quantity of matter in an object; measure of
inertia that an object exhibits in response to any effort
made to start or stop state of motion. SI unit Kg.
3. Newton: SI unit of force; amount of force needed to
accelerate 1 kg of mass at a constant acceleration.
1 N=9.8 m/s2
4. Normal Force: the supportive force that is
perpendicular “normal” to the surface—vertical
direction.
Newton’s Second Law
of Motion
FORCE AND
ACCELERATION
• C. Newton’s 2nd Law of Motion
• Law explains what happens when there is
either a single applied force or 2 more applied
forces whose vector sum is NOT zero.
• (Forces are what produce acceleration)
• Law states: “the effect of an applied forced is to
cause the body to accelerate in the direction of
the force.”
• The acceleration is in direct to proportion to
the force & inversely proportional to the mass
of the body.
• (Combination of forces act on objects & it is the
net force (Fnet) that accelerates the object).
• If a body is at rest & a force acts on the body,
then the body will move in the direction of the
force applied & will move faster while the force
is continued.
• If a body is moving in a straight line & force
acts, then the force will increase the speed
while force acts & it will move in the direction
of the force.
• Therefore, velocity changes & acceleration is
not zero. If different forces are applied to the
object, the magnitude of the acceleration will
be directly proportional to the amount of force.
But, will be inversely proportional to the mass.
• Example: net force doubled, acceleration
doubled. Mass doubled, then acceleration…
• D. Solving Force vectors
• Equilibrium is the state of body in which there
is no change in its motion. A body in
equilibrium is either at rest or moving at
constant speed in a straight line.
• When there are NO unbalanced forces acting
on a body, the vector sum of all the forces
acting on the body is zero.
• So each force is equal to the other. To find the
equilibrant of the 2 concurrent forces (acting at
the same time), find the vector first.
• Since the equilibrant must balance the effect of
the resultant, the equilibrant must have the
same magnitude but different & opposite
direction.
• Equilibrant force is the single force that if
applied at the same point produces
equilibrium.
FORCES CAUSE
ACCELERATION
There is always MORE than
one force acting on an
object at one time.
Forces are found in
“pairs”.
5.2 Mass Resists
Acceleration
As the mass of an object
increases, the ability to
accelerate it using the
same force decreases.
Think about a grocery cart…
When the cart is empty, it is
easy to push.
The cart easily accelerates
with simple pushing.
What about when the cart is
full and the mass is greater?
(see example)
The higher the mass of the cart,
the harder you have to push.
What is different with the 2
carts?
5.3 Newton’s Second Law
Using variables, we get the
equation:
F
A = m
Because we always use the
same units, we can also
say…
Net Force
Acceleration =
Mass
DUE TODAY:
• Newton’s 2nd law Notes (KEEP)
• Balloon Rocket Qs
“The whole secret of life is to be
interested in one thing profoundly and
in a thousand things well.”
Horace Walpole
DUE NEXT CLASS:
• Newton’s 2nd law worksheet
• Bring Calculator!