Download I. What is Motion? a. Motion - is when an object changes place or

I.
What is Motion?
a. Motion - is when an object changes place or position. To properly
describe motion, you need to use the following:
1. Start and end position?
2. Movement relative to what?
3. How far did it go?
4. In what direction did it go?
b. Distance – the length of the path or route traveled between two
points, how far something moves
c. Displacement – the distance and direction along the shortest path an
object has moved from its starting point
Label the following line segments as distance or displacement.
II.
Speed and Velocity
a. Speed – the distance traveled divided by the time interval during
which the motion occurred, calculated as distance divided by time
• s = d/t
• t = d/s
• d=sxt
 A bird is observed to fly 50 meters in 7.5 seconds. Calculate the
speed of the bird in m/s.
 A race car travels 300km in 2 hours. What is the race car’s
speed?
1. Constant speed - the same change in distance is traveled every
second.
2. Average speed – found by dividing the total distance traveled
by the time taken.
3. Instantaneous speed – the speed of an object at one instant of
time.
b. Velocity – tells you both speed and direction of an object’s movement.
Velocity is the change in position divided by the change in time.
III.
Acceleration and Momentum
a. Acceleration - the rate at which the velocity of an object changes
with time, calculated as the change in velocity divided by time
b. A change in velocity (acceleration) can be an increase in speed,
decrease in speed, or a change in direction.
1. An increase in velocity is commonly called positive acceleration.
2. A decrease in velocity is commonly called negative acceleration,
or deceleration.
a = (sf – si) / t
 A jet starts at rest at the end of a runway and reaches a speed of 80
m/s in 20 s. What is its acceleration?
 A skateboarder is moving in a straight line at a speed of 3 m/s and
comes to a stop in 2 sec. What is his acceleration?
c. Momentum – describes the tendency of objects to keep going in the
same direction with the same speed.
 Momentum = mass x velocity
p=mxv

A car is traveling at a velocity of 13.5 m/sec north on a straight
road. The mass of the car is 1,300 kg. A motorcycle passes the car
at a speed of 30 m/sec. The motorcycle (with rider) has a mass of
350 kg. Calculate and compare the momentum of the car and
motorcycle.
d. Law of conservation of momentum – any time objects collide, the total
amount of momentum is the same before and after the collision.
Total p = p1 + p2

A train car moving to the right at 10 m/s collides with a parked
train car. They stick together and roll along the track.
If the moving car has a mass of 8,000 kg and the parked car has a
mass of 2,000 kg, what is their total momentum after the
collision?

IV.
What is the combined velocity of the trains after the collision?
Force
a. Force – any push or pull on an object resulting from an objects
interaction with another object, measured in newtons (N)
1. Net force – the combination of all the forces action on an
object
2. Balanced forces – When two or more forces exerted on an
object and their effects cancel each other out, the motion of
the object does not change.
3. Unbalanced forces – When two or more forces act on an object
and the net force is not zero, the motion of the object changes.
+1 N
-1 N
+1N
-2N
+2 N
+2 N
b. Friction – a force that resists motion between two surfaces that are
touching each other
1. Three types of friction
a. Static friction – force caused by the attraction between
the atoms on the two surfaces that are touching each
other
Examples:
V.
VI.
VII.
b. Sliding friction – force that is caused by two objects
rubbing against each other
Examples:
c. Rolling friction – force which opposes the motion of one
object rolling over another
Examples:
2. Reducing friction – friction can wear down objects or resist
motion to the point of not allowing parts to move, causing them
to not function properly. To reduce friction, we can use
lubricants.
Examples:
Newton’s First Law of Motion
a. Newton’s first law of motion – an object at rest remains at rest, and
an object in motion remains in motion at a constant speed and in a
straight line unless acted on by an unbalanced force.
1. Inertia – tendency of objects to resist changes in motion
2. Newton’s first law is sometimes called the “Law of Inertia”
Newton’s Second Law of Motion
a. Newton’s second law of motion – the acceleration of an object depends
on the mass of the object and the amount of force applied
1. Mass – the amount of matter something contains
2. Acceleration – the rate at which the velocity of an object
changes with time
a = Fnet / m
F = ma
 Two dogs play tug of war. Each dog exerts a force on the rope.
The first dog (24) pulls with a force of 10N to the left and the
second dog (32kg) pulls with a force of 12N to right. What is the
net force? What is the acceleration of the dogs?
 What is the force necessary to accelerate 1,250kg car at a rate of
40m/s2?
Newton’s third law of motion
a. Newton’s third law of motion – forces always act in equal but opposite
pairs. For every action, there is an equal but opposite reaction.
VIII.
IX.
Gravity
a. Gravity is the force of attraction between objects.
1. The bigger the mass of an object the bigger its force of
gravity.
2. The sun has a very large mass, so exerts a large pull of gravity
on everything in the solar system.
3. The sun's gravity holds the planets in orbit around it.
4. The planets do not fall towards the sun because they are
moving sideways at high speed.
Mass and Weight
a. How are mass and weight different? To understand the differences
we need to compare a few points:
1. Mass is a measurement of the amount of matter something
contains, while Weight is the measurement of the pull of
gravity on an object.
2. Mass is measured by using a balance comparing a known amount
of matter to an unknown amount of matter. Weight is measured
on a scale.
3. The mass of an object doesn't change when an object's location
changes. Weight, on the other hand does change with location.
b. To determine weight, we can substitute the acceleration of the
gravitational force for acceleration
F=mg (force = mass x acceleration of gravity)
1. On Earth, the acceleration of gravity (g) is equal to 9.8 m/s2
downward, which rounded is 10 m/s2downward
2. On the moon, = 1.6 m/s2
3. On Venus, g = 8.83 m/s2
4. On Jupiter, g = 26.0 m/s2
1 newton = 0.225 pounds force


A girl has a mass of 42kg, what is her weight on Earth in N and
pounds?
What is her weight in N and pounds on the moon? Venus? Jupiter?