Some Physics Vocabulary

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Acceleration = a change in speed: Speeding up…Slowing down… or changing direction.

Centripetal Force = The push or pull on a moving object toward the center of its curved path. Centripetal force is a net force.

Force = A push or pull that one object exerts on another object.

Gyroscopic Inertia = "A body that is set spinning has a tendency to keep spinning in its original orientation." For example, a top or gyroscope will not fall over when it is spinning.

Kinetic energy = The energy of a moving body. Kinetic energy = 1/2mv2.

Law of Conservation of Momentum = "In a system consisting of bodies on which no outside forces are acting; the total momentum of the system remains the same."

Momentum can be transferred from one object to another.

In an interaction, the momentum lost by one mass equals the momentum gained by the other.

Total Momentum before interaction = The Total Momentum after.

A net force is the sum of all forces acting on an object. A net force is capable of accelerating a mass. For instance, if the wheels of a car push it forward with 5 Newtons and drag is 3 Newtons, the net force is 2 Newtons, forward. Motion to the right is positive. Motion to the left is negative.




Newton's First Law of Motion (Law of Inertia) ="Every object remains in a state of rest or of uniform motion in a straight line unless acted upon by an outside (net)  force."

Objects at rest remain at rest.

Objects in motion remain in motion in a straight line (unless acted upon by an outside force.)

Things keep doing what they were doing until interrupted!


Newton's Second Law of Motion (Force net = mass x acceleration) (Fnet = ma)

"When a force acts upon a body it accelerates that body in the direction of the force. The acceleration produced is directly proportional to the force and inversely proportional to the mass of the body."

Objects move in the direction they are pushed or pulled.

It is easy to push or pull lighter masses.

It is harder to move larger masses.

Things accelerate more quickly when a greater force is used.


Newton's Third Law of Motion = "For every action or force there is an equal and opposite reaction or force."

Any time you touch an object, it is touching you with the same amount of force. Forces always come in equal and opposite pairs. This means that the forces are equal even when a big object crashes into a small object.

Force = - Force

mass x acceleration = - mass x acceleration


Newton's Law of Gravitation (Inverse Square Law) = "Any two bodies in the universe attract each other with a force that is directly proportional to their masses and inversely proportional to the square of their distance apart. (If the distance between 2 objects is doubled, the force of gravity falls to 1/4 of its former value.)"

Gravity depends on the mass of objects and the distance between them!

Potential energy = Energy that is stored. Energy of position or state. Gravitational PE = mgh.  PE of a rubber band = 1/2kx2 

Rotational Inertia = the property of an object that resists any change in its state of rotation. If at rest, it tends to remain at rest; if rotating, it tends to remain rotating and will continue to do so unless interrupted. For example, think of a metal ring and a solid disk, each with the same mass. The metal ring has its mass at the perimeter and therefore has more rotational inertia than the solid disk. Thus, the ring resists rolling from a state of rest.

Speed = Distance/Time

Velocity = Speed and direction

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