Science Term 2 Physics

Distance

Distance

The total length of the path taken by an object between the origin and the destination point. A scalar quantity.

Displacement

The direct length between any two points when measured along the minimum path between them. A vector quantity.

Scalar

A quantity with magnitude only.

Vector

A quantity with magnitude and direction.

Magnitude

The general quantity or distance (the extent or size of something).

Speed

The rate at which something moves. The rate of change of distance over time. A scalar quantity. Can be instantaneous (at any given point in the trip) or average (overall). S = D/T.

Velocity

The rate of change in displacement of an object over time. A vector quantity. V = D/T.

Acceleration

The rate of change in velocity. Can be negative (eg. going from 6 m/s/s to 1 m/s/s) or positive (eg. going from 1 m/s/s to 6 m/s/s).

Distance-time graphs

Graphs that represent the distance travelled by a moving object over time. The gradient represents the speed of an object (the steeper the gradient, the faster). If the line is straight, the object is moving at a constant speed. If it is curved, it is either accelerating or decelerating. To find the overall speed of an object over time: speed = change in distance/change in time.

Velocity-time graphs

Graphs that represent the velocity of a moving object over time. The gradient represents the acceleration of an object. If the line is straight, the object is moving at a constant speech. If is diagonal, it is accelerating uniformly or decelerating uniformly. To find the acceleration: acceleration = change in velocity/change in time. The area under a velocity time graph gives the total distance travelled.

Newton’s 1st Law

An object at rest stays at rest and an object in motion stays in motion with the same speech in the same direction unless acted upon by an unbalanced force.

Force

A push or pull upon an object resulting from the object’s interaction with another object.

Friction

The force resisting the relative motion of things sliding against each other.

Normal force

The force that surfaces exert to prevent solid objects from passing through each other.

Weight

The force acting on an object due to gravity.

Mass

A measure of inertia (how much matter is in an object).

Inertia

An object’s tendency to resist changes in its motion (heavy objects are harder to change motion (a larger force is required) therefore more inertia, light objects are easier to change motion (a smaller force is required) therefore less inertia).

Newton’s Second Law

Looks at the relationship between an object’s mass, acceleration, and force. An unbalanced force acting upon an object causes it to accelerate. The rate of acceleration is directly related to the size of the force applied (eg. doubling the force acting upon an object will double the acceleration). Therefore, force is directly proportional to acceleration. Applying a force to an object with a small mass yields a greater acceleration (eg. doubling the mass of an object will halve the acceleration). Large mass = small rate of acceleration. Therefore, the rate of acceleration is inversely proportional to the mass of an object. F = mass x acceleration (mass in kg and acceleration in m/s/s). Weight is a gravitational force exerted on an object by an astronomical body measured in Newtons. Gravity causes objects to accelerate towards Earth at a rate of approximately 9.8m/s/s. Weight = mass x 9.8.