Title: Motion and Forces
1Motion and Forces
2Bell Work 1/26/11
- Copy each of these statements onto your bell work
sheet. Then decide if they are true or false.
If false correct them. - Speed includes direction, while velocity does
not. - A moving object covers the same distance in less
time if its velocity is greater. - Acceleration measures only change in speed.
3Bell Work 1/22/10
- Please begin working on your foldable or
PowerPoint - On your bell work sheet write down working on
project for today
4Bell Work 1/27/11
- Please answer 1-13 in the MAP practice packet by
the sinks. Write your answers for each question
on your bell work sheet for today. PLEASE DO NOT
WRITE IN THE PACKET
5Force 2.1 Notes
- forces occur when one object pushes or pulls on
another object - We say that one object exerts a force on another
object to cause it to accelerate.
6Describing Forces
- forces are describe according to
- strength and
- direction
7Two types of Forces
- Unbalanced Force
- two forces acting in the same direction
- OR
- One stronger force acting in the opposite
direction of a weaker force. - Unbalanced forces cause an object to accelerate!
8- Balanced Force
- equal forces acting in opposite directions
- balanced forces will NOT change the objects
motion!
9Newtons First Law
- An object at rest will remain at rest unless
acted upon by an unbalanced force!
10continued
- An object moving at constant velocity will
continue moving at constant velocity unless acted
upon by an unbalanced force.
11Inertia Lab Questions
- Before you start this experiment, see if you can
decide which egg is the raw one and which egg is
the hard boiled one. Place the eggs on the two
plates and start them spinning at the same time.
The egg that continues spinning for the longest
time is the hard boiled egg. - Steps for the 1st experiment
- 1. Place the uncooked egg on a plate and start it
spinning. 2. Touch it lightly with your
fingertip to stop the egg spinning.3. Once the
egg stops take your finger away immediately. - What happens to the egg? The shell of the egg
actually stops spinning but the inside (yolk and
egg white) keeps spinning. Because the inside of
the raw egg is a liquid, it makes the egg start
to spin again. This force is called inertia. - Steps for the 2nd experiment
- 1. Place the hard-boiled egg on a plate and start
it spinning.2. Touch it lightly with your
fingertip to stop the egg spinning.3. Once the
egg stops take your finger away immediately. - What happens to the egg? The boiled egg stops
spinning because the inside contents of the egg
are a solid mass. - Steps for the 3rd experiment
- 1. Place both eggs on the plates (one on each
plate). 2. Start both eggs spinning at the same
time.3. Place your finger on each egg at the
same time to quickly stop them spinning.4. Let
go of both eggs at the same time. - Now you can compare how the hard-boiled egg stops
spinning and the raw egg keeps spinning.
12Law of Inertia
- Newtons first law is often referred to as the
Law of Inertia. - Inertia is a property that describes an objects
resistance to changes in motion. - if an object is moving, inertia keeps it moving.
- if an object is at rest, inertia keeps it at
rest.
- Mass is the amount of matter in an object.
- Mass is a measure of inertia.
- the more mass an object has the more inertia it
has. This means it will take more force to get
it to accelerate. - the opposite is also true less mass, less
inertia, less force. - mass is measured in grams.
13How are mass and inertia related?
- The more matter in an object, the harder it is to
get the object to accelerate or you could say the
harder it is to overcome the objects inertia.
14Bell Work 1/28/11
- Please answer 1, 2, and 4 on page 47 in the book.
15Bell Work 1/31/11 choose the correct word to
fill in the blanks force, inertia, motion, net
force, Newtons first law, unbalanced force
- _______ is the change of position over time.
- The overall force acting on an object when all
forces are combined is called _____ - A force that can change the motion of an object
is called a(n) ________. - A(n) _______ is a push or a pull.
- Objects at rest remain at rest, and objects in
motion remain in motion at the same velocity,
unless acted on by an unbalanced force. This
statement describes ____. - The resistance of an object to a change in speed
or direction is called_______.
16Force 2.2 Notes
- Newtons Second Law of Motion
- Explains a relationship between force, mass and
acceleration - Often expressed as force mass x
acceleration - Simply stated An objects acceleration depends
on the mass of an object and the strength and
direction of the force acting on it.
17Force mass x acceleration
- Units
- acceleration m/s/s
- mass kg
- force kg x m/s/s or Newton (N)
18Practice
- If a 5 kg ball is accelerating 1.2 m/s2, what is
the force on it? - A person on a scooter is accelerating 2m/s2. If
the person has a mass of 50 kg, how much force is
acting on that person?
19- 3. If a team pulls with a combined force of 9000N
on an airplane with a mass of 30,000kg what is
the acceleration of the airplane? - 4. Half the people on the team decide not to pull
the airplane. The combined force of those left
is 4500 N, while the airplanes mass is still
30,000 kg. What is the acceleration?
20- 5. A model rocket is accelerating at 2 m/s2. The
force on it is 1 N. What is the mass of the
rocket? - 6. A boy pushes a shopping cart with a force of
10 N, and the cart accelerates 1 m/s2. What is
the mass of the cart?
21- Centripetal force any force that keeps an
object moving in a circle
22Bell Work 2/7/11 Please use the back of the bell
work sheet from last week
- What is Newtons First Law of motion?
- What is Newtons Second Law of motion?
- Give an example of centripetal force.
23Bell Work 2/8/11
- A model rocket is accelerating at 6 m/s2. The
force on it is 2 N. What is the mass of the
rocket? - Another model rocket that has a mass of 15 kg is
accelerating at 5 m/s2. What is the force being
applied to the rocket? - A girl pushes a 10 kg shopping cart with a force
of 30 N. What is the acceleration of the cart?
24Force Notes 2.3
- Newtons Third Law states that for every action
there is a reaction
25Bell Work 2/9/11
- Identify the action/reaction force pair involved
when you catch a ball. - Explain the difference between balanced forces
and action/reaction forces. - A man pushes on a wall with a force of 50 N. What
are the size and the direction of the force that
the wall exerts on the man?
26Force 2.4 Notes
- Objects in motion have momentum. Which would have
more momentum a bowling ball being thrown at a
wall or a tennis ball? - Momentum A measure of mass in motion. The
momentum of an object is the product of its mass
and velocity - Formula to calculate momentum
- Momentum mass x velocity
- p mv
27(No Transcript)
28Momentum Calculations
- Example 1 - What is the momentum of a 1.5 kg ball
moving at 2 m/s? - Example 2 A 6 kg ball is moving with a velocity
of 2 m/s. What is the balls momentum? - Example 3 What is the momentum of a 0.5 kg ball
moving at 0.5 m/s?
29 Momentum is a property of a moving object.
30Momentum can be transferred from one object to
another
- If two objects involved in a collision have very
different masses, the one with the less mass has
a greater change in velocity. - Collision a situation in which two objects in
close contact exchange energy and momentum - What happens with 2 bumper cars?
31 Forces in collisions are equal and opposite.
32Momentum is conserved
- Conservation of momentum states that the total
momentum of a system of objects does not change,
as long as no outside forces are acting on that
system.
33 Momentum is conserved in collisions.
34Bell Work 2/10/11
- Complete 11-16 on page 71. You only have to
write the letter of the answer.
35Bell Work 2/16/11
- Give an example of each of Newtons 3 Laws. Make
sure to explain in detail how each example
relates to Newtons Laws.
36Bell Work 2/17/11
- Write complete sentences!
- What is the difference between the momentum of
bowling ball and a baseball that are moving at
the same velocities? - What is the difference between a balanced force
and an unbalanced force? - Please get out your study guide and review for
the test.