Download PRENTICE HALL SCIENCE EXPLORER

PRENTICE HALL SCIENCE EXPLORER
PHYSICAL SCIENCE
CHAPTER 10
FORCES
10-1 The Nature Of Force
Objectives:
 Explain how a force is described.
 Demonstrate how unbalanced and balanced forces relate to an object’s motion.
A. What Is Force?
1. A _______________________________ is a push or pull applied to an object.
2. Like velocity and acceleration, a force is described by its ___________________________ and by
the _______________________________ in which it acts.
3. The magnitude (strength) of a force is measured by the SI unit called the _________________ (N).
4. The Newton named after the English scientist, Sir Isaac Newton.
B. Combining Forces
1. Intro.
a.) The combination of all forces acting on an object is called the _________________________.
b.) When two forces act in the same direction, the net force can be found by _________________
the forces together.
c.) When forces act in different directions along the same line, one of them is _________________.
d.) In this situation, the net force is the ___________________________ of the two.
2. Unbalanced Forces
a.) When forces acting on an object are ____________________, a net force is applied to the object.
b.) _________________ forces acting on an object result in a _________________force and cause a
change in the object’s _________________.
3. Balanced Forces
a.) _________________ forces acting on an object in opposite directions are called
_________________ forces.
b.) Balanced forces result in _________________ change of motion for the object.
10-2 Friction And Gravity
Objectives:
 Tell what factors determine the strength of the friction force between two surfaces.
 List what factors affect the gravitational force between two objects.
 Explain why objects accelerate during free fall.
A. Friction
1. The Causes of Friction
a.) Friction is a force between two objects that _________________ motion of both objects.
b.) The strength of the force of friction depends on two factors:
i.) How _________________ the forces push together.
ii.) The _________________ of surfaces involved.
2. Static Friction
a.) The friction acting on objects that are not moving is called ______________________________.
b.) Static friction must be __________________________________ in order to produce motion.
c.) __________________________- is the friction acting on objects that are sliding on one another.
3. __________________________________– is the friction acting on objects when one object is
rolling across the surface of another.
4. __________________________________– occurs when a solid object is moving through a fluid.
5. Of the four types of friction, __________________________________is greatest.
B. Gravity
1. Universal Gravitation
a.) Gravity is a force that pulls objects __________________________________ each other.
b.) __________________________________explained the Law of Universal Gravitation.
c.) The Law of __________________________________ states that the force of gravity acts
between all objects in the universe.
2. Factors Affecting Gravity
a.) The two factors that affect the force of gravity are ________________ and _________________.
b.) The _________________ the mass, the _________________ the force of gravity.
c.) The ________________ the distance between the objects, the ___________ the force of gravity.
3. Weight and Mass
a.) _________________________ is the measure of the force of gravity acting upon an object.
b.) Mass the amount of __________________________________ in an object.
c.) On the moon, you would weigh about _____________ of what you weigh on Earth because
Earth is _________________ times more massive than the moon.
C. Gravity And Motion
1. Free Fall
a.) When the only force acting on an object is gravity, the object is said to be in
_______________________________________.
b.) When in free fall, an object is accelerated toward Earth at _________________.
c.) All objects in free fall accelerate ______________________________regardless of their masses!
2. Air Resistance
a.) Air resistance is the ________________________ experienced by objects falling through the air.
b.) Air resistance _____________________________ as velocity increases.
c.) When air resistance and the force of gravity become _________________, an object stops
accelerating and falls at a ______________________________ velocity.
d.) The maximum velocity that an object can reach in free fall is called its
__________________________________ velocity.
3. Projectile Motion
a.) An object that is thrown or launched horizontally is called a _____________________________.
b.) Projectiles undergo __________________________________ motion.
c.) An object launched __________________________________will fall at the same rate as if it
were dropped ___________________________________________________.
10-3 Newton’s First And Second Laws
Objectives:
 State Newton’s First Law of Motion
 State Newton’s Second Law of Motion
A. The First Law Of Motion
 An object at rest will remain at rest, and an object moving at a constant velocity will continue
moving at a constant velocity, unless it is acted upon by an unbalanced force.
1. _________________ – is the tendency of an object to resist a change in motion.
2. Inertia Depends on Mass – the _________________ the mass, the greater the _________________.
B. The Second Law Of Motion
 The acceleration of an object is dependent upon the mass of the object and the force acting on it.
1. Determining Acceleration
a.) To calculate the _________________ of an object, you divide the _________________ acting
on the object by its _________________.
𝑁𝑒𝑡 𝐹𝑜𝑟𝑐𝑒
b.) 𝐴𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 = 𝑀𝑎𝑠𝑠
2. Changes In Force And Mass
a.) ________________________ the force acting on an object also _________________________
the acceleration.
b.) ________________________ the mass of an object _____________________ the acceleration.
10-4 Newton’s Third Law
Objectives:
 State Newton’s Third Law of Motion
 Explain how you can determine the momentum of an object.
 State the Law of Conservation of Momentum
A. Newton’s Third Law Of Motion
 If one object exerts a force on anther object, then the second object exerts an equal force on
the first object in the opposite direction.
1. Action-Reaction Pairs
a.) When you jump, you _________________ against the ground and the _________________ in
turn pushes against you.
2. Detecting Motion – You cannot always detect motion when action _________________________
are at work.
3. Do Action-Reaction Forces Cancel?
a.) Action-Reaction Forces do not cancel out because although the forces are equal, they are acting
on __________________________________ objects.
b.) Examples: Volleyball pg. 355
B. Momentum
1. __________________________________ is a characteristic of a moving object that is related to the
_________________ and the ____________________________ of the object.
2. Newton called momentum a “______________________________________________.”
3. 𝑀𝑜𝑚𝑒𝑛𝑡𝑢𝑚 = 𝑀𝑎𝑠𝑠 𝑥 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦
C. Conservation Of Momentum
 The Law of Conservation of Momentum states that the total momentum of any group of
objects remains the same, or is conserved, unless outside forces act on the objects.
1. Collisions With _________________ Moving Objects
2. Collisions With _________________ Moving Object
3. Collisions With _________________ Objects
10-5 Rockets And Satellites
Objectives:
 Explain how a rocket lifts off the ground.
 Explain what keeps a satellite in orbit.
A. How Do Rockets Lift Off?
1. A rocket can rise into the air because the __________________________________ with a
downward action force exert an equal but opposite reaction force on the _____________________.
B. What Is A Satellite?
1. A __________________________________ is any object that orbits another object in space.
2. ___________________________________________________– is caused by centripetal force.
3. Satellite Motion – Satellites in _________________ around Earth continuously fall toward Earth,
but because Earth is curved they travel around it.
4. Satellite Location
a.) At an orbit altitude of _________________ and above the equator a satellite remains at the same
point above the surface of Earth.