Chapter 1: Matter in Motion

When you witness an object that is moving, you are comparing it with something that is not moving (background). A frame of reference is a stationary background or point used to describe something that is moving. Example: The Earth is the most common one

A change in position of an object over a certain amount of time is called motion. When describing motion, you are always comparing it with some frame of reference.

Speed is the rate at which an object moves. The faster the rate of motion, the faster the speed! Formula: Speed = distance / time

Because we use the metric system, speed is usually measured in meters (m) or kilometers (km) per hour.

Example: Michael Phelps holds the world record for the 200 meter freestyle in 1:42 (102 seconds). What is his average speed? Speed = Distance / Time Speed = 200 m / 102 sec Speed = 1.96 m/sec

Velocity is the speed of an object in a given direction. Velocity is used to measure both speed and direction of motion.

The rate of change in velocity is known as acceleration The rate of change in velocity is known as acceleration. This can be speeding up, slowing down, or changing direction. Formula: Acceleration = change in velocity / time

Example: A 1988 Ford Mustang GT accelerates from 0 km/hr to 135 km/hr in 12.5 seconds. What is the rate of acceleration? Acceleration = change in velocity / time Acceleration = 135 km/hr / 12.5 seconds Acceleration = 10.8 km/hr/sec

If there is a decrease in velocity, than the value of acceleration is negative. Negative acceleration is called deceleration.

A force is a push or pull that gives energy to an object. This energy causes the object to start moving, stop moving, or change direction.

Forces that are in opposite directions and equal in size are called balanced forces. Example: tug of war with equal teams   When 2 forces are balanced, there is no change in motion!

Forces that are in opposite directions and unequal in size are called unbalanced forces. Example: tug of war with unfair teams

Friction is a force that acts in the opposite direction of motion Friction is a force that acts in the opposite direction of motion. Friction will cause a moving object to slow down and finally stop.

The amount of friction depends on: 1.    how hard the 2 surfaces are forced together 2. the type of surface involved

When 2 solid objects are sliding past each other, the type of friction that results is called sliding friction.

The friction produced by objects such as wheels or ball bearings is called rolling friction. In general, rolling friction tends to be less than sliding friction.

A final type of friction is called fluid friction A final type of friction is called fluid friction. This occurs when an object moves through a fluid (liquid or gas).

The acceleration of a falling object is due to the force of gravity between the object and the Earth.

Gravity is the force of attraction between 2 objects that depends on the mass of the objects and the distance between them. On Earth, the force of gravity is 9.8 m/sec/sec

Law of Universal Gravitation All objects in the universe attract each other by gravitation. The strength of the gravity between two objects increases as the masses of the objects increases. Every object in the universe is under the influence of some form of gravity! Gravity Comparisons Sun: 28 times Earth Jupiter: 2.7 times Venus: 0.9 times Pluto: 0.04 times

The size of the force depends on: 1.    the mass of the objects 2. the distance between them

Weight is a measure of the force of gravity on an object Weight is a measure of the force of gravity on an object. Weight is different than mass! Weight is measured in Newtons (N). Formula: Weight = Mass x Acceleration due to gravity Note: acceleration due to gravity is 9.8 m/sec/sec