Unit 5 Study Guide Physical Science

Motion

The change in position of an object from one place to another.

Reference Point

An object used to determine motion; it is usually a stationary object. (i.e., house, trees, earth)

Speed

The distance traveled divided by the time interval during which the motion occurred. (Formula Speed=distance/time) (Units meters/second)

Velocity

The distance traveled divided by the time interval during which the motion occurred WITH direction. (Formula Velocity = distance/time with direction. (Units = meters/seconds w direction)

Acceleration

The rate at which velocity changes over time. (Formula Acceleration = final velocity - starting velocity /time) (Units = meters/seconds/second/ or meters/ second squared)

3 Ways for an Object to Accelerate

Speed Up, Slow Down, Change Direction

Force

A push or a pull

Newton

The unit used to measure force

Net Force

The combination of all forces acting on an object

Balance Forces

When the forces on an object create a ZERO net force. Do not cause a change in motion.

Unbalanced Forces

When the forces on an object DO NOT create a ZERO net force. Will cause an object to speed up, slow down or change direction.

Friction

A force that opposes motion between two surfaces that are in contact. Rough surfaces cause more friction than smooth surfaces.

3 Types of Friction

Sliding, Rolling (wheels), Fluid (moving through gas or liquid)

Ways to Reduce Friction

Put it on Wheels, Use a lubricant, Smooth the surface, Remove mass

Gravity

A force of attraction between objects because of their masses.

Law of Universal Gravitation

States that all matter in the universe is attracted to all other matter.

Factors that Determine Gravitational Attraction

Mass (greater mass means greater gravity), Distance (the closer to the objects the greater the attraction)

Weight and Mass

Mass is universal, it stays the same, but weight can change due to differences in gravity, (i.e., the moon and earth have different gravitational forces).

Gravitational Constant

The rate at which things accelerate due to gravity. On Earth, the Gravitational Constant is 9.8 m/s/s.

The formula for Acceleration Due to Gravity

Change in velocity = 9.8 m/s/s x time (secs). Example 9.8 m/s/s x 5 secs = 49 m/s

Air Resistance

A force that opposed the downward motion of a falling object.

Terminal Velocity

The point where gravity's downward force is balanced by the upward force of air resistance. The object continues to fall, but its velocity no longer increases.

Newton's 1st Law

The law of Inertia. An object at rest stays at rest, an object in motion stays in motion at a constant speed in a straight line unless acted upon by an unbalanced force.

Newton's 2nd Law

Force = mass x acceleration Newtons = Kg. x m/s/s

Newton's 3rd Law

Action/Reaction. For every action, there is an equal and opposite reaction. Force act in pairs.