Motion
Reading: Textbook Chapter 11 p.362 - 391
Measuring Motion
Motion is the change in an object's position in relation to a reference
point or stationary object. Distance measures the path taken by an object that changes position.
Displacement is the change in an objects position. Distance may or may not be a straight
line and does not indicate direction. Displacement must be in a straight line and must always indicate the
direction, such as 12 blocks toward the school.
Speed is the distance traveled divided by the time interval during which
the motion occurred. It describes how fast an object moves.
Average Speed = distance/ time
v = d / t
Instantaneous speed is the speed at a given point in time.
Velocity is the speed of an object and the direction of motion.
Resultant velocity is the combination of two velocities.
Acceleration
Acceleration is the rate at which velocity changes over time. Acceleration is a change
in speed, direction or both. Uniform circular motion is constant acceleration.
acceleration = final velocity - initial velocity
time
a = fv-iv /t
Go to assignments and do questions 1-5.
Motion and Force
Force is an action exerted on an object in order to change the state of rest
or motion. Balanced forces do not cause a change in the objects motion, the net force is zero. Unbalanced forces
do not cancel the opposite force, but moves in the direction of the net force. Friction is a
force that opposes motion between two surfaces that are in contact. Static friction is the force
that resists the initiation of sliding motion between two surfaces in contact and at rest. Kinetic
friction is the force that opposes the movement of two surfaces that are in contact and sliding over
each other.
Energy, Forces
and Motion are explained for you at this website.
Harmful friction can be reduced.
1. lubricants
2. change sliding friction to rolling friction
3. make rough surfaces smooth
Helpful friction can be increased.
1. make smooth surfaces rough
2. increase the force of one surface
Go to assignments and do question 6-8.
Forces
Read Chapter 12 p. 394 - 423.
Laws of Motion - Sir Isaac Newton
1. An object at rest remains at rest and an object in motion maintains its velocity unless it experiences
an unbalanced force. Inertia is the tendency of an object at rest to remain at rest or, if
moving to continue moving at a constant velocity. Inertia is related to an object's mass. Mass is the measure
of inertia.
"Matter resists any change in motion."
2. The unbalanced force acting on an object equals the object's mass times its
acceleration. Force is measured in newtons.
force = mass x acceleration
F = ma
3. For every action force, there is an equal and opposite reaction force. Forces always occur
in pairs. Force pairs do not act on the same object. Equal forces don't always have equal effects. Moving
objects have momentum.
Go to the Physics
Classroom and learn more about Newton's Laws and what the animations.
Go to assignments and do questions 9-10.
Momentum is the mass times the velocity of an object.
momentum = mass x velocity
p = mv
Law of Conservation of Momentum states the total amount of momentum in an
isolated system is conserved. Momentum is transferred to the second object. Conservation of momentum explains
rocket propulsion. The upward push on the rocket is equal to the downward push on the exhaust gases.
Law of Universal Gravitation states that all objects in the universe attract
each other through gravitational force. All matter is affected by gravity. Gravitational force increases as mass
increases. Gravitational force decreased as distance increases.
Free fall or "g" is when only the force
of gravity is acting on the body. Near Earth's surface, g is
approximately 9.8 m/s2. Weight is equal to mass times free-fall acceleration. Orbiting objects
are in free fall. Two motions, forward motion and free fall, combine to cause orbiting.
weight = mass x free-fall acceleration
w = mg
Terminal velocity is the constant velocity of a falling object when the
force of air resistance is equal in magnitude and opposite in direction to the force of gravity.
Projectile motion is the curved path that an object follows when thrown,
launched, or projected near the surface of the earth. Projectile motion has some horizontal and some vertical
motion.
Go to assignments and do questions 11-13.
When finished you may play
Lunar Lander .
Assignments
1. Do practice problems on p.369 in the Physical Science textbook. Go to
go.hrw.com and enter the keyword HK8MP to do more problems.
2. A caterpillar just finished eating a leaf that took him 7 minutes to eat and now is traveling along
a tree branch. . It has traveled 42 cm from the last leaf it ate looking for another leaf. The caterpillar
has reached the next leaf, 6 minutes later. What measurements are necessary to find the average speed of the
caterpillar? What unit of mesaure will be used for the speed? What is the caterpillar's average speed? Write
the answer in terms of speed and velocity.
3. Do the Practice problems on p. 375 of the Physical Science textbook.
4. Joshua skates in a straight line at a constant speed for one minute, then begins going in circles at
the same rate of speed, and then finally begins to increase speed. When is he accelerating? Explain you answer
telling why you think he is accelerating at those points.
5. Graph the velocity of a car accelerating at a uniform rate from 7.0 m/s to 12.0 m/s in 2.0 s.
Calculate the acceleration. (Hint: Velocity m/s 0-15 should be the vertical axis and time 0-2 should be the
horizontal axis.)
6. Describe three ways friction was important on your way to school today. ( not a list, sentences)
7. Do questions 1-4 on p.385 of the Physical Science textbook.
8. As a new driver you will encounter decisions that have to be made in an brief moment. For example,
you come upon a traffic light turning yellow. You must decide whether to stop or go on through. Discuss the
variables you must consider when making your decision. Use the terms force, acceleration, and velocity in
you answer.
9. Describe Newton's 3 Laws of Motion in your on words and give a real world example of each.
10. Express Newton's Second Law matematically. Do Practice questions p. 401 and
questions 6-7 on p. 402 in the Physical Science textbook.
11. Explain why you weight would be less on the moon than on Earth even though you mass would not change.
Use the law of universal gravitation in you explanation. Explain the difference between mass and weight.
12. For each pair, determine whether the objects have the same momentum. If the objects have different
momentums, determine which object has more momentum and why.
a. a car and train that have the same velocity
b. a moving ball and a still bat
c. two identical balls moving at the same speed in the same direction
d. two identical balls moving at the same speed in opposite directions
13. Complete the Practice on p. 415 in the Physical Science textbook.
13. Complete the graph on p. 423 #24 in the Physical Science textbook.
Chapter Review
Chapter 11-12 test
KV NewSchool Learning 
