# Topic 5 - Forces Flashcards

What are scalar quantities?

Scalar quantities only have a magnitude (size).

What are vector quantities?

Vector quantities have a magnitude and a direction.

What is the difference between speed and velocity?

Speed is a scalar quantity, so it only has a magnitude. Velocity is a vector quantity, so it has a magnitude and and a direction.

What is the equation for speed?

Speed = distance / time - s = d/t - m/s = m / s

What is the unit for speed?

metres per second - m/s

What does the calculations of speed assume?

It assumes the speed is constant.

Give examples of vector quantities?

Acceleration, force, displacement and velocity.

Give examples of scalar quantities?

Temperature, mass, energy, distance and speed.

What is the equation for acceleration?

Acceleration = change in velocity / time - a = Δv / t - m/s^2 = Δv / seconds

What is the unit for acceleration?

metres per second squared - m/s^2

How do we work out the resultant force?

We use Pythagoras’ Theorem.

What is the unit for the resultant force?

Newtons - n

What is displacement?

Displacement is the distance an object moves in a straight line from a starting point to a finishing point.

Is displacement a scalar or vector quantity?

Displacement is a vector quantity as it contains a direction and a magnitude.

What is distance?

Distance is how far an object moves.

Is distance a scalar or vector quantity?

Distance is a scalar quantity as it contains a magnitude but not a direction.

What is a force?

A force is a push or pull that changes an objects motion.

What are the two forces?

Contact forces and non-contact forces.

What are contact forces?

Contact forces are forces that act between two objects that are physically touching.

What are non-contact forces?

Non-contact forces happen when objects are separated.

What are examples of contact forces?

Friction, air resistance, tension and normal contact force.

What are examples of non-contact forces?

Gravitational force, electrostatic force and magnetic force.

What is an interaction pair?

An interaction pair is a set of 2 forces that are equal and opposite, acting on 2 interacting objects.

What is air resistance?

Air resistance comes about when an object moves through air and collides with molecules. This creates a force that slows the object down.

What is tension?

Tension is the pulling force that a string or cable exerts (creates) when something or someone pulls on it.

What is the normal contact force?

When you push on a table, your hand doesn’t move through it. This is because the normal contact force from the table pushes equally on your hand.

What is friction?

Friction comes about whenever two surfaces are touching and try to move against each other. Tiny bumps in the surface interlock (overlap or fit together). This creates a frictional force that opposes their motion.

What is on the x-axis of a distance time graph?

The time (seconds) is on the x-axis of a distance-time graph.

What is on the y-axis of a distance time graph?

The distance (metres) is on the y-axis of a distance-time graph.

What happens when the line of a distance time graph is increases horizontally but not vertically?

The object is stationary.

How do we work out distance in a speed-time graph?

We work out the area below the line.

What is mass?

The mass of an object is a measure of the amount of matter it contains. The mass of an object is constant.

What is inertia?

Inertia is how difficult it is to change the object’s motion depending on the objects mass.

How does the mass of an object tell you how much inertia it has?

An object with a high mass has more inertia than an object with a lower mass.

What is the equation for weight?

Weight = mass x gravitational field strength - w = mg - newtons = kg x n/kg

What is the centre of mass?

The centre of mass is the point through which an object’s weight appears to act.

Where is the centre of mass in a hanging object?

If an object is hung from a string, it will hang with its centre of mass directly below the point that it is hung from.