Transcript velocity - Gallatin Gateway School

Newton’s Second Law
Created by: Faith Cohen/2009
VELOCITY
The word scientists use to
describe how fast an object is
moving
Velocity is measured as:
a change in distance per change in
time
change in distance
change in time
What are some examples of objects
that move at high velocities?
What are some examples of objects that
move at low velocities?
Scientists have a special way to
measure a change in velocity:
Acceleration
Acceleration is a change in
velocity.
The Way Acceleration Works:
 If you’re speeding up, you have
positive acceleration.
 If you’re slowing down, you have
negative acceleration.
 If you’re changing speed quickly,
you have high acceleration.
 If you’re changing speed slowly, you
have low acceleration.
Example:
You’re driving along in your car
and suddenly have to slam on
your brakes for a red light. Is
the acceleration high or low? Is
it negative or positive?
High negative acceleration because
you’re slowing down quickly.
Example:
It’s your first space
takeoff. Suddenly the
rockets fire and you’re
on your way to the
Space Center. Identify
the acceleration.
High positive acceleration because you’re
speeding up quickly.
Example:
You’re driving down the
highway when your car
runs out of gas and you
slowly roll to a stop on the
side of the road. Identify
the acceleration.
Low negative acceleration because you’re
slowing down slowly.
Example:
You’re walking to class when you
realize you’re running just a little
bit late. You start walking a bit
fast, but you still hope to make it on
time. Finally the bell rings so you
break into a jog and then a run,
trying to get to class before the
teacher notices you’re late.
Low positive acceleration because you’re
speeding up slowly.
If you’re driving a car and
want to speed up, what
do you do?
If you’re riding a Big
Wheel bike and want to go
faster, what do you do?
If you want to win the race
and you are behind, what
do you do?
Pushing pedals, pressing accelerators, and
running are all examples of forces.
1) A force is anything that
changes the velocity of an
object.
2) A change in velocity is
acceleration, so . . . therefore
3) A force is anything that gives
an object acceleration.
Nothing will change speed
unless acted upon by a force.
If it’s sitting still, it will keep
sitting still. If it’s moving
fast, it will keep moving fast.
Only a force can change the
velocity of an object.