Physics Vocabulary

Closed system

A system is closed if no energy flows across the boundary and there is no outside work done. (p. 175)

Joule

Abbreviated as J. SI unit of energy. 1J=m2v2 (p. 102)

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

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.

Force

a push or pull exerted on an object, measured in Newtons (N)

Reference point

a visible object to which you can compare the change of distance to a moving object

Centripetal acceleration

acceleration of an object toward the center of a curved or circular path

Mass

amount of matter in an object, measured in grams (g) or kg (kilograms)

Gravity

attractive force between two objects that depends on the masses of the objects and the distance between them

Speed

distance an object travels per unit of time.

Kinetic energy

energy a moving object has because of its motion; depends on the mass and speed of an object

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

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

Friction

force that opposes the motion between two touching surfaces

Sliding friction

force that opposes the motion of two surfaces sliding past each other.

Rolling friction

force that opposes the sliding motion between a rolling object and the surface it rolls on.

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

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.

Centripetal Force

net force exerted toward the center of a curved path

Negative acceleration

rate of change of velocity where the velocity is decreasing

Positive acceleration

rate of change of velocity where the velocity is increasing

Acceleration

rate of change of velocity, acceleration = (final velocity -initial velocity)/ (final time-initial time)=meters/second2

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.

Other Types of energy

sound, thermal, light, electrical, chemical, nuclear

Instantaneous speed

speed of an object at a given point in time.

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

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.

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

Potential Energy

stored energy

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

Mechanical energy

sum of potential and kinetic energy in a system

Energy

the ability to cause a change

Projectile motion

the curved path associated with an object that is thrown near the earth's surface

Static friction

the force that prevents two surfaces from sliding past each other.

Velocity

the speed and direction of a moving object, can change with change in speed and/or direction

Net force

the sum of two or more forces on an object that are pushing or pulling in the same or opposite direction

Average speed

total distance an object travels divided by the total time it takes to travel that distance, speed=distance/time

Newton

unit of force, N=(mass in kilograms)(acceleration due to gravity)= (mass in kilograms)(9.8meters/second2)

Momentum

usually given the symbol p. Property of a moving object that equals its mass times its velocity.