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Physics Study Guide
Chapter 1 Section 1 summary
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An object is in motion if it changes position over time in relation to a reference point.
Speed is the distance traveled by an object divided by the time the object takes to travel that
distance.
Velocity is speed in a given direction.
Acceleration is the rate at which velocity changes.
An object can accelerate by changing speed, direction, or both.
Speed can be represented on a graph of distance versus time.
Acceleration can be represented by graphing velocity versus time.
Chapter 1 Section 2 summary
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A force is a push or a pull. Forces have size and direction and are expressed in newtons.
Force is always exerted by one object on another object.
Net force is determined by combining forces. Forces in the same direction are added. Forces in
opposite directions are subtracted.
Balanced forces produce no change in motion. Unbalanced forces produce a change in motion.
Chapter 1 Section 3 summary
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Friction is a force that opposes motion.
Friction is caused by hills and valleys on the surfaces of two objects touching each other.
The amount of friction depends on factors such as the roughness of the surfaces together.
Two kinds of friction are kinetic friction and static friction.
Friction can be helpful or harmful.
Chapter 1 Section 4 Summary
 Gravity is a force of attraction between objects that is due to their masses.
 The law of universal gravitation states that all objects in the universe attract each other through
gravitational force.
 Gravitational force increases as mass increases.
 Gravitational force decreases as distance increases.
 Weight and mass are not the same. Mass is the amount of matter in an object. Weight is a measure
of the gravitational force on an object.
Chapter 2 Section 1 Summary
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Gravity causes all objects to accelerate toward Earth at a rate of 9.8 m/s₂
Air resistance slows the acceleration of falling objects. An object falls at its terminal velocity when
the upward force of air resistance equals the downward force of gravity.
An object is in free fall if gravity is the only force acting on it.
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Objects in orbit appear to be weightless because they are in free fall.
A centripetal force is needed to keep objects in circular motion. Gravity acts as a centripetal force to
keep objects in orbit.
Projectile motion is the curved path an object follows when thrown or propelled near the surface of
Earth.
Projectile motion has two components – horizontal motion and vertical motion. Gravity affects only
the vertical motion of projectile motion.
Chapter 2 Section 2 Summary
Newton’s first law of motion states that the motion of an object will not change if no unbalanced
forces act on it.
Objects at rest will not move unless acted upon by an unbalanced force.
Objects in motion will continue to move at a constant speed and in a straight line unless acted upon
by an unbalanced force.
Inertia is the tendency of matter to resist a change in motion. Mass is a measure of inertia.
Newton’s second law of motion states that the acceleration of an object depends on its mass and
on the force exerted on it.
Newton’s second law is represented by the following equation: F = m x a.
Newton’s third law of motion states that whenever one object exerts a force on a second object,
the second object exerts an equal and opposite force on the first object.
Chapter 2 Section 3 Summary
 Momentum is a property of moving objects.
 Momentum is calculated by multiplying the mass of an object by the object’s velocity.
 When two or more objects collide, momentum may be transferred, but the total amount of
momentum does not change. This is the law of conservation of momentum.
Chapter 5 Section 1 Summary
 Energy is the ability to do work, and work equals the transfer of energy. Energy and work are
expressed in units of joules (j).
 Kinetic energy is energy of motion and depends on speed and mass.
 Potential energy is energy of position. Gravitational potential energy depends on weight and height.
 Mechanical energy is the sum of kinetic energy and potential energy.
 Thermal energy and sound energy can be considered forms of kinetic energy.
 Chemical energy, electrical energy, and nuclear energy can be considered forms of potential energy.
Chapter 5 Section 2 Summary
 An energy conversion is a change from one form of energy to another. Any form of energy can be
converted into any other form of energy.
 Kinetic energy is converted to potential energy when an object is moved against gravity.
 Elastic potential energy is another example of potential energy.
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Your body uses the food you eat to convert chemical energy into kinetic energy.
Plants convert light energy into chemical energy.
Machines can transfer energy and can convert energy into a more useful form.
Chapter 5 Section 3 Summary
 Because of friction, some energy is always converted into thermal energy during an energy
conversion.
 Energy is conserved within a closed system. According to the law of conservation of energy, energy
cannot be created or destroyed.
 Perpetual motion is impossible because some of the energy put into a machine is converted into
thermal energy because of friction.