Flashcards(Forces)

Force

A push, pull or twist caused by interaction between two objects.

What unit is force measured in?

Newtons (N)

What instrument measures force?

Spring balance / Newton meter

What can a force do to an object?

Change speed, direction, shape, size or cause rotation.

What are the two main categories of forces?

Contact forces and non-contact (field) forces.

What are contact forces?

Forces where objects must touch each other.

Give examples of contact forces.

Friction, tension, compression, push, pull.

What are field forces?

Forces that act at a distance without touching.

Examples of field forces

Gravitational, magnetic and electrostatic forces.

What is friction?

A force that resists motion between surfaces in contact.

When does static friction occur?

When the object does not move.

When does kinetic friction occur?

When the object moves.

What are the three types of kinetic friction?

Sliding, rolling and fluid friction.

What is sliding friction?

Friction when two surfaces slide over each other.

Examples of sliding friction

Rubbing hands together, pushing furniture.

What is rolling friction?

Friction when a round object rolls over a surface.

Examples of rolling friction

Wheels, bowling balls, soccer balls.

What is fluid friction?

Friction when an object moves through a liquid or gas.

Examples of fluid friction

Swimming, airplanes flying, birds flying.

Advantage of friction

Allows us to walk without slipping.

Disadvantage of friction

Produces heat and causes wear.

What is tension?

A pulling force transmitted through a rope, string, cable or wire.

How does tension act?

It pulls equally on objects at opposite ends.

Symbol for tension

T

What is compression force?

A pushing force that squeezes or compacts an object.

Symbol for applied/compression force

FA

Examples of objects under compression

Columns, disc brakes, gaskets.

What is normal force?

The perpendicular force exerted by a surface on an object.

Direction of normal force

Perpendicular (90°) to the surface.

Symbol for normal force

FN or N

How are forces represented graphically?

With arrows showing size and direction.

What does the arrow length show?

The size (magnitude) of the force.

What does the arrowhead show?

The direction of the force.

What are balanced forces?

Equal forces acting in opposite directions on the same object.

Resultant force of balanced forces

0 N

Effect of balanced forces

No visible change in motion.

What are unbalanced forces?

Forces of different sizes acting in opposite directions.

Effect of unbalanced forces

The object changes speed or direction.

What is resultant force?

The overall force after adding all forces together.

What is gravitational force?

The force of attraction between masses.

What affects the size of gravitational force?

Mass and distance between objects.

How does mass affect gravity?

Larger mass gives greater gravity.

How does distance affect gravity?

Greater distance gives weaker gravity.

What is weight?

The gravitational force acting on an object.

Unit for weight

Newtons (N)

What is mass?

The amount of matter in an object.

Unit for mass

Kilograms (kg) or grams (g)

Does mass change in different places?

No, mass always stays the same.

Does weight change in different places?

Yes, weight depends on gravity.

What is gravitational field strength?

Force per unit mass exerted by gravity.

Unit for gravitational field strength

N/kg

Average gravitational field strength on Earth

9,8 N/kg

What is the formula for weight?

Fg = m × g

What does Fg stand for?

Weight

What does m stand for?

Mass

What does g stand for?

Gravitational field strength

What does directly proportional mean?

As one value increases, the other increases at the same rate.

Symbol for directly proportional

∝

How is mass measured?

With a scale.

How is weight measured?

With a spring balance or Newton meter.

Why is weight less on the Moon?

The Moon has a weaker gravitational field strength.

How much weaker is gravity on the Moon?

About 6 times weaker than Earth.

What happens when resultant force is zero?

The forces are balanced.

What happens when resultant force is not zero?

The forces are unbalanced.

What are non-contact forces also called?

Field forces.

What is electrostatic force?

A force between electrically charged objects.

What is magnetic force?

A force between magnets or magnetic materials.

Can a force have no visible effect?

Yes.

Can forces change an object's direction?

Yes.

Can forces change an object's shape?

Yes.

Can forces cause rotation?

Yes.