Reference point
a visible object to which you can compare the change of distance to a moving object
Speed
distance an object travels per unit of time.
Average speed
total distance an object travels divided by the total time it takes to travel that distance, speed=distance/time
Instantaneous speed
speed of an object at a given point in time.
Velocity
the speed and direction of a moving object, can change with change in speed and/or direction
Terminal velocity
a free-falling object achieves its terminal velocity when the downward force of gravity equals the upward force of wind resistance. This causes the net force on the object to be zero, resulting in an acceleration of zero.
Momentum
usually given the symbol p. Property of a moving object that equals its mass times its velocity.
Acceleration
rate of change of velocity,
acceleration = (final velocity -initial velocity)/
(final time-initial time)=meters/second2
Positive acceleration
rate of change of velocity where the velocity is increasing
Negative acceleration
rate of change of velocity where the velocity is decreasing
Centripetal acceleration
acceleration of an object toward the center of a curved or circular path
Projectile motion
the curved path associated with an object that is thrown near the earth's surface
Force
a push or pull exerted on an object, measured in Newtons (N)
Net force
the sum of two or more forces on an object that are pushing or pulling in the same or opposite direction
Balanced forces
forces on an object that are equal in size and opposite in direction, resulting in a net force of 0 N
Unbalanced forces
forces on an object that do NOT result in a net force of 0 N
Centripetal Force
net force exerted toward the center of a curved path
Newton
unit of force, N=(mass in kilograms)(acceleration due to gravity)= (mass in kilograms)(9.8meters/second2)
Isaac Newton
British physicist, mathematician, and astronomer Sir Isaac Newton (1642-1727) stated Laws of Motion to describe the effects of forces on the motion of objects
Newton's First Law of Motion
states that an object moving at a constant velocity keeps moving at that velocity (in other words, an object in motion stays in motion) unless an unbalanced force acts on it, often referred to as the Law of Inertia where body at rest tends to stay at rest
Inertia
resistance of an object to change in its motion, the greater mass an object has, the greater it will resist changes in motion; Therefore, more massive objects have greater inertia.
Newton's Second Law of Motion
states that the acceleration of an object is in the same direction as the net force on an object, and that the acceleration equals the net force divided by the mass. acceleration=Force/mass -> Force=ma
Newton's Third Law of Motion
states that for every action force there is an equal and opposite reaction force. In other words, when one object exerts a force on a second object, the second object exerts a force on the first that is equal in strength and opposite in direction.
Friction
force that opposes the motion between two touching surfaces
Fluid friction
force that opposes motion through a fluid (air or liquid). Air resistance, the force that opposes the motion of objects that move through the air, is a form of fluid friction
Rolling friction
force that opposes the sliding motion between a rolling object and the surface it rolls on.
Sliding friction
force that opposes the motion of two surfaces sliding past each other.
Static friction
the force that prevents two surfaces from sliding past each other.
Mass
amount of matter in an object, measured in grams (g) or kg (kilograms)
Weight
gravitational force exerted on an object. In other words, the measure of the pull of gravity on an object. Measured in Newtons (N). The weight of an object will change depending on the gravity exerted on it.
Closed system
A system is closed if no energy flows across the boundary and there is no outside work done. (p. 175)
Gravity
attractive force between two objects that depends on the masses of the objects and the distance between them
Energy
the ability to cause a change
Potential Energy
stored energy
Elastic Potential Energy
energy stored by something that can stretch or compress, such as a rubber band or spring
Chemical Potential Energy
energy stored in chemical bonds
Gravitational potential energy
stored energy an object has due to its position. where m is mass, g is the acceleration of gravity, and h is height
Kinetic energy
energy a moving object has because of its motion; depends on the mass and speed of an object
Mechanical energy
sum of potential and kinetic energy in a system
Other Types of energy
sound, thermal, light, electrical, chemical, nuclear
Joule
Abbreviated as J. SI unit of energy. 1J=m2v2 (p. 102)