Grade 8: Forces and Motion

The Big Idea: Forces have _______________and __________________.

Magnitude and Direction

motion

the change in position relative to a reference point

reference point

an object that helps you detect motion in another object

speed

distance traveled by an object divided by the time the object takes to travel that distance

velocity

speed in a given direction

acceleration

rate at which velocity changes over time

friction

A force that opposes motion between two surfaces that are in contact

Kinetic friction

"moving friction" can be sliding or rolling

Static friction

"non-moving friction"

Friction (Helpful vs. Harmful)

Helpful- brakes on a car; sandpaper on wood; tread on a tire

Harmful - wearing of parts, rubbing a hole in a shoe or sock;

inertia

tendency of matter to resist a change in motion; mass is a measure of inertia

force (in science)

any push or pull; represented in Newtons (N); has both magnitude and direction

pressure

force exerted on a given area; measured in pascals

Newton's 1st Law of Motion

An object that is moving or at rest does not change it's state unless acted on by an unbalanced force.

Newton's 2nd Law of Motion

Acceleration of an object increases as the force on the object increases.

Newton's 3rd Law of Motion

For every force there is an equal and opposite force.

momentum

a combination of inertia (mass) and velocity (speed and direction)

net force

the sum of all forces acting on an object

balanced forces

objects may be moving or non-moving; net force is 0; the objects will not accelerate.

unbalanced forces

objects may be moving or non-moving; net force is not 0; objects will accelerate in the direction of the force.

Archimedes' principle

states that the buoyant force on an object is equal to the weight of the fluid displaced by the object

Bernoulli's principle

states that fluid pressure decreases as the speed of the fluid increases

fluid

any non-solid material that flows and takes the shape of its container (includes all gasses and liquids)

Pascal's principle

states that a change in pressure in an enclosed fluid is transmitted equally to all parts of the fluid.

fluids flow from areas of _________ pressure to areas _________pressure

high, low

Fluid pressure _________________ as depth ___________________.

increases, increases