Physics

A. MOTION

•Velocity and speed
The velocity of an object is the rate of change of its position in a particular direction.

Speed is the magnitude of velocity expressed in distance covered per unit of time.

Changes in velocity can involve changes in speed or direction or both.

• Average speed = total distance traveled divided by the total time elapsed Formula: Speed = Distance/Time (S = D/T)
Familiar units for measuring speed: miles or kilometers per hour

B. FORCES

• The concept of force: force as a push or pull on an object
Examples of familiar forces (such as gravity, magnetic force)
A force has both direction and magnitude.
Measuring force: expressed in units of mass, pounds in English system, newtons in metric system
• Unbalanced forces cause changes in velocity.

If an object is subject to two or more forces at once, the effect is the net effect of all forces.

The motion of an object does not change if all the forces on it are in balance, having net effect of zero.

The motion of an object changes in speed or direction if the forces on it are unbalanced, having net effect other than zero.

To achieve a given change in the motion of an object, the greater the mass of the object, the greater the force required.

C. DENSITY AND BUOYANCY

• When immersed in a fluid (i.e. liquid or gas), all objects experience a buoyant force.
The buoyant force on an object is an upward (counter-gravity) force equal to the weight

of the fluid displaced by the object.
Density = mass per unit volume
Relation between mass and weight (equal masses at same location have equal weights)

• How to calculate density of regular and irregular solids from measurements of mass and volume

The experiment of Archimedes
• How to predict whether an object will float or sink

D. WORK

• In physics, work is a relation between force and distance: work is done when force is exerted over a distance.

Equation: Work equals Force x Distance (W = F x D)
Common units for measuring work: foot-pounds (in English system), joules (in metric

system; 1 joule = 1 newton of force x 1 meter of distance)

E. ENERGY

• In physics, energy is defined as the ability to do work.

• Energy as distinguished from work

To have energy, a thing does not have to move.

Work is the transfer of energy.
• Two main types of energy: kinetic and potential

Some types of potential energy: gravitational, chemical, elastic, electromagnetic

Some types of kinetic energy: moving objects, heat, sound and other waves • Energy is conserved in a system.

F. POWER

• In physics, power is a relation between work and time: a measure of work done (or energy expended) and the time it takes to do it.

Equation: Power equals Work divided by Time (P = W/T),

or Power = Energy/Time Common units of measuring power: foot-pounds per second, horsepower

(in English system); watts, kilowatts (in metric system)