Early Work – Mar. 26
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Transcript Early Work – Mar. 26
Early Work – Mar. 26
List five forces you encountered during
break.
Foldables
Create the foldable on the front page of
ch. 4
Read section 1
P103: 1 - 7
Early Work – Mar. 28
If an object of mass 3 kg has an
acceleration of 5 m/s2, what force is
acting on it?
Write the three forms of the equation for
Newton’s Second Law.
To Get Done (10 minutes)
Some of you haven’t finished your ch. 3
tests!!
Homework – if done show teacher and
then put in InBox
Activity
On a blank sheet of paper,
What is inertia?
How are inertia and Newton’s First Law related?
If an object has a mass of 40 kg and a force of 10
N acts on it, what will the object’s acceleration be?
If an object has a mass of 10 kg and is being
accelerated at the rate of 1.5 m/s2, what force is
acting on it?
If a 25 N force accelerates an object at 12 m/s2,
what is the mass of the object?
Activity Cont’d
Draw a picture of the apparatus.
Predict what you think will occur when
the pie tin is hit with a broom.
What occurred?
4.2 - Gravity
Early Work – Mar. 30
What are the two types of friction we
discussed?
Define inertia.
Gravity
An attractive force between any two
objects that depends on the masses of
the objects and the distance between
them
Earth is the only thing close enough and
large enough to us to feel it’s gravitational
attraction
Universal Gravitation
Law that enables us to calculate the
gravitational attraction between any two
objects
m1m2
F =G 2
d
Earth’s Gravity
Earth attracts everything at the same
rate (or pulls it with the same
acceleration)
Earth’s gravity accelerates objects at
9.8 m/s2
When in free fall (like from being
dropped), the force on an object can be
calculated by F = ma or F = mg.
Weight
Even when not in free fall, Earth still has
it’s pull on you. It causes you to be
exerting a force on what you are sitting
or standing on.
That force is called weight.
W = mg
Weight v. Mass
Weight is a force (measured in N)
Mass is the measure of the amount of
matter present (measured in kg or g)
Let’s weigh ourselves
Use table on page 107
Projectiles
Projectile – anything thrown or launched
Earth’s gravity causes projectiles to arc
downward
Centripetal Force
Centripetal Acceleration – acceleration
toward the center of a curved or circular
path
Centripetal Force – the force exerted
towards the center of the path
Hmwk
P111 – 1 – 3, 6
Early Work – Apr. 3
If every object has its own gravity, why is
it that we are not attracted (literally) to
each other?
Have homework out and ready to grade
Worksheet
Complete p20
Complete sections 1 and 2 on p19
Newton’s Third Law
Action-reaction pairs
To every action force there is an equal
and opposite reaction force
• When you jump on a trampoline, for
example, you exert a downward force on
the trampoline.
• Simultaneously, the trampoline exerts an
equal force upward, sending you high into
the air.
Rocket Propulsion
• In a rocket engine, burning fuel
produces hot gases. The rocket
engine exerts a force on these
gases and causes them to
escape out the back of the
rocket.
• By Newton’s third law, the
gases exert a force on the
rocket and push it forward.
Momentum
• A moving object has a property called
momentum that is related to how much
force is needed to change its motion.
The momentum of an object is the
product of its mass and velocity.
Conservation of Momentum