Download Motion and Forces

Motion and Forces
How we use physics in everyday
life
Warm up 4/12/12
1. How can you figure out how fast something is
going?
2. How would you define the word speed?
3. What factors would you consider to determine
the speed of an object?
For example: Size? Weight? Color?
Announcements
• If you received a letter informing your parents
about your academic progress, you MUST have
it signed and returned by Friday, April 13th.
• You also need to make sure each of your teachers
are signing a progress record for you at the end
of each core class.
Intro to physics
• Physics is the study of matter and its motion
through space and time, along with related
concepts such as energy and force.
• We already know that matter is anything that
has mass and takes up space.
• During this unit, we will learn more about how
matter moves using energy and different forces.
What is speed?
• Speed is the measure of how fast or how far
something moves within a given amount of time.
• The higher the speed of an object, the faster that
object changes its position.
• In other words, the higher the speed of an object
the faster it moves!
How do we calculate speed?
• In order to find out the speed of an object, you
must first determine its distance and time.
• Thus, speed is:
Speed = Distance of an object
Time traveled
Or S= D
T
Example 1
A wheel chair racer completes a 100 meter course in
20 seconds. What is his speed?
Steps:
1. Ask yourself what do you know?
Distance= 100 meters
Time= 20 seconds
2. What do you want to know?
Speed
3. s=d
s= 100 s=5 meters per second or m/s
t
20
Guided practice
1. A man runs 200 meters in 25 seconds. What is
his speed?
2. If you travel 100 meters in 50 seconds, what is
your speed?
3. Suppose a race is 50 meters, and it takes an
athlete 15 seconds to run it. Is this enough
information to calculate the runners speed?
What is velocity?
• Velocity is speed in a specific direction.
• For example, you are in a train travelling east at
75 miles per hour you are describing the trains
velocity.
• In order to determine the velocity of an object,
you need to know its speed and its direction.
Example 1
Vector
• Velocity is an example of a vector.
• A vector is defined as a quantity that has both
size and direction.
• Speed is NOT a vector because it is a measure of
how fast or slow an object moves, which is not a
direction.
• Velocity has a size and direction and is therefore
considered to be a vector.
Velocity vs. Speed
• Because velocity includes direction, its possible
for two objects to have the same speed but
different velocities.
Exit slip (quiz grade) complete on NBK
paper
1. What is the formula for speed?
2. What two things do you need to know to
calculate velocity?
3. Carlos lives 100 meters away from home. What
is his average speed if he reaches his friends
house in 50 seconds? (show your work)
4. True or false: Velocity is NOT considered a
vector.
Warm Up 4/13/12
1. What is the formula for speed?
2. In order to determine the velocity of an object
you must know what ___________ it is
travelling.
3. A ___________ is defined as a quantity that
has both size and direction.
4. Velocity is an example of a____________.
Announcements
• If you received a letter informing your parents
about your academic progress, it is due today!
Hand it in to me now if you have it 
• You also need to make sure each of your teachers
are signing a progress record for you at the end
of each core class.
Review of exit slips
1. What is the formula for speed? S=d/t
2. What two things do you need to know to
calculate velocity? Speed and direction of
movement
3. Carlos lives 100 meters away from home. What
is his average speed if he reaches his friends
house in 50 seconds? (show your work) see
board
4. True or false: Velocity is NOT considered a
vector. False
Speed practice problems/Lab
With a partner, you will be calculating speed.
Once you and your partner are done, you will be
allowed to complete the speed lab.
Both sheets must be submitted to get full credit
