Transcript force - Cloudfront.net

Describing Force and
Motion
***Copy everything on
slides 1-7 and then watch
the rest of the slides.***
1. What is
FORCE and
how is it
measured?
• A push or pull
applied to an
object
• Measured in
Newtons (N)
• Measured with a
spring scale
2. How are
forces
described?
10N
10N
Net force = 0
no motion
20N
10N
Net force = 10N
to the right
20N
10N
Same direction so …
net force = 30 N
to the right
*net force –
combination of all
forces acting on
an object
• Balanced forces – all
forces acting on an
object are equal
– There is NO MOTION
• Unbalanced forces –
one or more forces acting
on an object are stronger
than others
– There is MOTION
3. What are
SPEED and
VELOCITY and
how are they
calculated?
*Speed is the distance an
object travels in a unit of
time. 50 km/hr
*Velocity is SPEED in a
DIRECTION. 50 km/hr
west
• Sp = d/t
• V = d/t include direction
4. What is
MOTION?
• Occurs when an object
changes position relative to
a reference point
5. What is
Newton’s First
Law? (Law of
Inertia)
Will stay at rest
until force acts
upon it.
– An object at rest stays at
rest and an object in motion
stays in motion unless
acted on by an unbalanced
force
– Inertia – tendency of an
object to resist any change
in its motion
Gravity Will continue
Friction
in motion until
these forces or
the wall stops it
6. What is
Newton’s
Second
Law?
• Net force acting on
an object causes the
object to accelerate
in the direction of the
force.
Force = mass X acceleration
F = m x a or a = f/m
or
m = f/a
7. What is
Newton’s
Third Law?
• For every action,
there is an equal
and opposite
reaction.
REACTION
ACTION
The truck is in motion. What is the force
that causes it to stop?
The push of the stopped car.
The car is at rest. What is the force that
causes it to move?
The push of the truck.
What about the ladder on top of the truck?
The ladder is in motion because the truck is in
motion.
When the truck stops, the ladder stays in motion.
The truck is stopped by the force of the car, but the
ladder is not.
What force stops the ladder?
Gravity.
The truck is in motion, the car is at rest. How do
each of these vehicles accelerate?
The truck stops moving. The car starts moving.
Which one will be the hardest to accelerate?
The truck because it has the most mass.
Why does the car move [accelerate] when it is hit
by the truck?
The heavy and moving truck has more force than
the small, at rest car.
Why does the truck stop moving when it hits the
car?
The force of the car pushing back on the truck,
plus the force of friction between the massive truck
and the road slow down, the stop the truck.
The truck hits the car. An action force stops the
truck.
What is the equal and opposite reaction force?
The force that pushes the car forward.