Download Newton*s Second Law

Newton’s Second Law
Newton’s First Law
WarmUp 10-2-12
• What effect does extra mass have on the
acceleration of an object if you don’t increase
force
1.WarmUp
2. SCIVID
3. Newton’s 2nd Law science notes
4. Mini Vid on 2nd Law
5. Jumping Force Game
WarmUp 10-22-12
• How does the gravitation force change as you
go from picture A to picture B (when the mass
decreases but distance stays the same)?
A. Increases
WarmUp
SciVid
3rd Law Poster
Bill Nye: Motion
B. Decreases
C. Stays the same
D. Doesn’t change
A
B
C
Newton’s Second Law
Newton’s Second Law Description
Newton’s Second Law Math
Short: Force= Mass x Acceleration
Example: How much force will you need to use to
push a pop machine that is 1000 kg with an
acceleration of 2 meters per second per second
Simple Rules:
1.
The greater the force that is applied to an object the
greater Acceleration it will have
F= ma
THE HARDER YOU PUSH THE MORE SOMETHING SPEEDS UP,
SLOWS DOWN, OR CHANGES DIRECTION
2. If Force is unchanged, then the greater the Mass of an object
the lower the acceleration will be
THE HEAVIER SOMETHING IS THE HARDER IT IS TO
MAKE SPEED UP, SLOW DOWN, CHANGE DIRECTION
Draw a situation
that describes the
two rules
Friction
Friction: This is
the force that
always opposes
motion.
F = 1000 x 2=
= 2000 N
If we pushed a box of kleenex ( 2kg) with the same
force ( 2000N) then what would our acceleration?
HINT: If not solving for force,
force is always on top
F=ma
A= F/m
M=F/a
A= F/M
A= 2000 N/ 2 kg
Three Types of Friction
Static Friction: Friction between two surfaces that are not moving
Rolling Friction: Friction between rolling object and a flat surface(least
amount of friction
Sliding Friction: Friction between flat surfaces where there is some
movement but force must be constantly applied
= 1000 m/s/s
3rd Law Poster
Newton’s Third Law
Short: Action/ Reaction
Long: For every action
force there is an equal
and opposite reaction
force
Example: A NASA rocket
shoots explosive gases into the
ground… the group pushes
back with the same
force(based on mass and
acceleration) and the rocket
exits the earth
More examples:
1.
Breaking hand by punching
someone in the face
2.
Any propulsion device
Person
Mass (kg)
Initial Force
Mass= Weight/ 9.8
This is also the
weight
Final Force(Final
F –Initial F)
Jumping Force
Jumping
Acceleration
(m/s/s)
A= Force/Mass
Mass x gravity
Gravity
Gravity: A force of attraction between two objects
Weight: The effect of gravity on an object
Weight = Mass x gravity
Big objects attract little objects
Time
Speed (m/s)
to them:
The average skydiver
hits his terminal
velocity at a speed of
56 m/s
When an object is in free fall
it is no longer accelerating
Acceleration
Distance
covered
1s
10
10
10
2s
20
10
30
30
10
60
4s
40
10
100
5s
50
10
150
6s
56
10
206
3s
Terminal velocity: highest
velocity a falling object
can reach due to
force air resistance = force
gravity
Mass
ALL OBJECTS FALL AT
THE SAME SPEED
TOWARDS THE EARTH
BUT SOME ARE
AFFECTED MORE BY
AIR.
Why does a feather fall at a different
speed than a hammer on earth but not
on the moon?
There is no air
resistance on
the moon!
Belongs to
an object(
always the
same)
Weight
Changes
depending on
the planet or
moon
Projectile Motion
What if one object object is shot
horizontally and another is dropped?
The only force acting on either ball
is GRAVITY so they fall at the same
rate and hit the ground at the
same time
1. At the same speed, which of the following
has the greatest inertia?
a. 1 kg
b. 2 kg
c. 5 kg
d.
10 kg
2. What will happen to an object
when a net force acts on it?
a. Fall
B. Stop
C. Accelerate
D. Go in a circle
3. According to Newton's 2nd law if you
double the mass of an
object and push with a constant force then the acceleration of that object will be
a.
b.
c.
d.
halved
unchanged
doubled
tripled
4. Two forces of 6 N and 3 N act upon an object in opposite directions. What is the net force
acting on the object? (See image below)
a. 3 N to the left
b. 3 N to the right
c. 9 N to the left
d. 9 N to the right
5. A truck with a mass of 1000 kg hits a wall and unloads a
force of 400,000 newtons. What is the negative acceleration of the trucks?.
a. - 0.0025 m/s2
b. - 0.025 m/s2
c. - 40 m/s2
d. - 400 m/s2
WARMUP QUIZ
10-5-12