Download Motion

Motion
The motion of an object can be measured. The
position of an object, its speed, and direction
can be represented on a graph. (C.S. 2.1, 3.2)
• Cheetahs are the fastest land mammals in the
world!
• It can cover 200 meters in 7 seconds (that is
half a lap on the track)
• It can accelerate from 0 to 29 meters per
second in 3 seconds!
• What does a cheetah have to do with our
lesson?
Motion & Speed
• Motion is simply a change of position
• Speed tells us how fast an object is moving.
The more distance a cheetah covers in a given
time, the greater his speed.
• If a cheetah can travel at a speed of 100 km
per hour and an ant can only cover 36 meters
in an hour- The cheetah has a greater speed.
Average Speed
• Average speed= distance
time
Memorize this formula.
You should already know it!
Calculate the average speed
• Suppose an airplane traveled 810 miles
between two cities. The elapsed time for the
trip was 3 hours. Calculate the speed of the
airplane.
Average speed= 810 miles
3 hours
When you do the math the speed of the average
speed of the plane is 270 miles per hour
Speed doesn’t always use mph
• Suppose a runner runs a race around a track
that is 400 meters. If the runner runs the race
in 40 seconds, what would be the runners
average speed?
Average speed= 400 meters
40 seconds
Do the math and 400 divided by 40 is 10 mps
Calculating Distance
• Suppose you are taking a trip by car. You can
travel about 50 mph on the roads you will be
using. You also know you can travel about 6
hours per day. You would like to know how far
you can go in one day. In other words you
NEED TO CALCULATE DISTANCE
Distance = speed x time
Distance = 50 x 6
So the answer is 300 miles
Calculating Time
• Suppose you have a job marking the lines on the
football field. The distance to be marked is 80
meters. You mark at a speed of 50 meters per
minute. How much time will it take you to mark
the whole line?
Time= distance
speed
Time = 80 meters
50m per 1 min
80/50 =1.6 minutes
First law of motion
• Stop/Start
– Friction
– Gravity
Newton’s first law of motion states that if no forces
acts on an object at rest, it will remain at rest. The
law also says that if the object is moving, it will
continue moving at the same speed and in the
same direction if no force acts on it.
Second law of motion
• Acceleration
– Speed
– Time
Newton’s Second Law of Motion says that the
amount of force needed to produce a given
change in the motion of an object depends on
the mass of the object. The larger the mass, the
more force is needed to give it a certain
acceleration.
Third law of motion
• Action
• Reaction
Newton’s Third Law of Motion says that if an
object exerts a force on a second object, the
second object will always exert a force on the
first object. This forces will be equal to the
force exerted by the first object. But the force
will be in the opposite direction. This law is
sometimes stated: For every action, there is
an equal and opposite reaction.
One last view of the cheetah
• Finish your worksheet using the formulas we
have learned today for
– Average speed
– Calculating time
– Calculating distance