Physics Midterm Terms

Terms and Definitions from the "Know the Definition of..." Section of the Midterm Study Guide

Displacement

Displacement

The change in an object’s position

Vector Quantity

A physical measurement that contains directional information

Scalar Quantity

A physical measurement that does NOT contain directional information

Velocity

The time rate of change of an object’s position (Δx/Δt)

Speed

The time rate of change of the distance traveled by an object (Δd/Δt)

Acceleration

The time rate of change of an object’s velocity (Δv/Δt)

Acceleration due to gravity on earth (metric)

9.8 m/sec^2

Acceleration due to gravity on earth (Imperial)

32 ft/sec^2

Free Fall

The motion of an object when it is falling solely under the influence of gravity

Parabolic Motion

Motion that occurs when an object moves in two dimensions but has zero acceleration in one of those dimensions and a constant, non zero acceleration in the other

Friction

A force that opposes motion, resulting from the contact of two surfaces

Newton’s First Law (The Law of Inertia)

An object in motion (or at rest) will tend to stay in motion (or at rest) until it is acted upon by an outside force

Newton’s Second Law

When an object is acted on by one or more outside forces, the vector sum of those forces is equal to the mass of the object times the resulting acceleration vector (ΣF=ma)

Prefixes for mass

Slugs, grams (mg, kg)

Prefixes for weight

Newtons, dynes, pounds

Normal Force

A force that results from the contact of two bodies and is perpendicular to the surface of contact

Kinetic Friction

Friction that opposes motion once the motion has already started

Static Friction

Friction that opposes the initiation of motion

Newton’s Third Law

For every action, there is an equal and opposite reaction

Translational equilibrium

An object is said to be in translational equilibrium when the sum of the forces acting on it is equal to zero

Two types of translational equilibrium

Static and Dynamic

Static Equilibrium

When an object is at rest

Dynamic Equilibrium

When an object moves with a constant velocity

Tension

the force from a tight string, rope, or chain. This force is directed away from the object to which the string, rope, or chain is anchored

Translational Motion

Motion from one point to another which does not involve repeatedly passing the same point in space

Rotational Motion

Motion around a central axis such that an object could repeatedly pass the same point in space relative to that axis

Axis of rotation

The point in space at the center of rotational motion

Lever arm

the length of an imaginary line drawn from the axis of rotation to the point at which the force is being applied

Torque

The tendency of a force to cause rotational acceleration. The magnitude of the torque is equal to the length of the lever arm times the component of the force that is applied perpendicular to it

Rotational Equilibrium

The state in which the sum of the torques acting on an object is zero