physics topic 1-3

What is a physical quantity?

A quantity that can be measured and given a numerical value and unit.

What is the SI unit of mass?

Kilogram (kg).

What is the SI unit of distance?

Metre (m).

What is the SI unit of time?

Second (s).

What is the SI unit of speed?

Metres per second (m/s).

What is the SI unit of acceleration?

Metres per second squared (m/s²).

What is the SI unit of force?

Newton (N).

What is the unit of gravitational field strength?

Newtons per kilogram (N/kg).

What is distance?

The total length of the path travelled by an object.

What is speed?

The distance travelled per unit of time.

What is the equation for speed?

Speed = distance ÷ time.

How can you calculate distance using speed and time?

Distance = speed × time.

How can you calculate time using distance and speed?

Time = distance ÷ speed.

What is average speed?

Total distance travelled divided by total time taken.

What is the equation for average speed?

Average speed = total distance ÷ total time.

What is a distance-time graph?

A graph showing how the distance travelled by an object changes with time.

What does the gradient of a distance-time graph represent?

Speed.

What does a horizontal line on a distance-time graph mean?

The object is stationary.

What does a straight sloping line on a distance-time graph mean?

The object is travelling at constant speed.

What does a steeper line on a distance-time graph mean?

The object is travelling faster.

What does a curve becoming steeper on a distance-time graph mean?

The object is speeding up.

What does a curve becoming less steep on a distance-time graph mean?

The object is slowing down.

How do you calculate speed from a distance-time graph?

Calculate the gradient by dividing the change in distance by the change in time.

What is the gradient of a graph?

The change in the vertical quantity divided by the change in the horizontal quantity.

What is acceleration?

The rate of change of velocity.

What is the equation for acceleration?

Acceleration = change in velocity ÷ time.

What is the full equation for acceleration?

a = (v − u) ÷ t.

What does u represent in the acceleration equation?

Initial velocity.

What does v represent in the acceleration equation?

Final velocity.

What does t represent in the acceleration equation?

Time taken.

What does a represent in the acceleration equation?

Acceleration.

What is deceleration?

Negative acceleration or a decrease in velocity.

Can an object accelerate while travelling at constant speed?

Yes, if its direction is changing.

Why can an object accelerate when its speed is constant?

Because a change in direction is a change in velocity.

What is velocity?

Speed in a specified direction.

What is a velocity-time graph?

A graph showing how an object's velocity changes with time.

What does the gradient of a velocity-time graph represent?

Acceleration.

How do you calculate acceleration from a velocity-time graph?

Calculate the gradient by dividing the change in velocity by the change in time.

What does a horizontal line on a velocity-time graph mean?

The object has constant velocity.

What does a horizontal line above zero on a velocity-time graph mean?

The object is travelling at constant positive velocity.

What does a line at zero on a velocity-time graph mean?

The object is stationary.

What does a positive gradient on a velocity-time graph mean?

Positive acceleration.

What does a negative gradient on a velocity-time graph mean?

Negative acceleration.

What does a line sloping down towards zero on a velocity-time graph mean?

The object is slowing down.

What does the area under a velocity-time graph represent?

Distance travelled.

How do you calculate distance from a velocity-time graph?

Calculate the area under the graph.

How do you calculate the area of a rectangle?

Width × height.

How do you calculate the area of a triangle?

½ × base × height.

How do you calculate the area of a trapezium?

½ × (sum of parallel sides) × height.

What is a force?

A push or pull that can change an object's motion, shape or direction.

What can a force do to an object?

It can change its speed, direction or shape.

What is a contact force?

A force that acts when two objects are physically touching.

What is a non-contact force?

A force that acts between objects without physical contact.

What is friction?

A force that opposes motion between surfaces in contact.

What direction does friction act?

Opposite to the direction of motion or attempted motion.

What is air resistance?

A force that opposes the motion of an object moving through air.

What is gravitational force?

The force of attraction between masses.

What is electrostatic force?

A force of attraction or repulsion between electrically charged objects.

What happens when two objects have the same type of electric charge?

They repel each other.

What happens when two objects have opposite electric charges?

They attract each other.

What is Newton's second law?

The acceleration of an object is proportional to the resultant force acting on it and inversely proportional to its mass.

What is the equation for Newton's second law?

F = ma.

What does F represent in F = ma?

Resultant force in newtons (N).

What does m represent in F = ma?

Mass in kilograms (kg).

What does a represent in F = ma?

Acceleration in metres per second squared (m/s²).

How do you calculate force?

Force = mass × acceleration.

How do you calculate mass using F = ma?

Mass = force ÷ acceleration.

How do you calculate acceleration using F = ma?

Acceleration = force ÷ mass.

What happens to acceleration if the resultant force increases while mass stays constant?

Acceleration increases.

What happens to acceleration if mass increases while resultant force stays constant?

Acceleration decreases.

What happens when the resultant force on an object is zero?

The object has no acceleration and its velocity remains constant.

What is weight?

The force acting on an object due to gravity.

What is the equation for weight?

W = mg.

What does W represent in W = mg?

Weight in newtons (N).

What does m represent in W = mg?

Mass in kilograms (kg).

What does g represent in W = mg?

Gravitational field strength in N/kg.

What is the difference between mass and weight?

Mass is the amount of matter in an object, while weight is the force acting on the object due to gravity.

Does mass change when an object moves to a different planet?

No, mass stays the same.

Can weight change when an object moves to a different planet?

Yes, because gravitational field strength can be different.

What is gravitational field strength?

The force acting per kilogram of mass.

What is the approximate gravitational field strength on Earth?

About 10 N/kg.

What is the unit of weight?

Newton (N).

What is the unit of mass?

Kilogram (kg).

What is the unit of gravitational field strength?

N/kg.

What is deformation?

A change in the shape or size of an object caused by a force.

What is stretching?

Deformation that makes an object longer.

What is compression?

Deformation that makes an object shorter.

What is extension?

The increase in length of an object when it is stretched.

What is the equation for extension?

Extension = final length − original length.

How do you calculate extension?

Subtract the original length from the stretched length.

What is elastic deformation?

Deformation where an object returns to its original shape and size when the force is removed.

What is inelastic deformation?

Deformation where an object does not return to its original shape and size when the force is removed.

What is Hooke's Law?

The extension of an elastic object is directly proportional to the force applied, provided the limit of proportionality is not exceeded.

What is the equation for Hooke's Law?

F = ke.

What does F represent in F = ke?

Force in newtons (N).

What does k represent in F = ke?

Spring constant in newtons per metre (N/m).

What does e represent in F = ke?

Extension in metres (m).

What is the spring constant?

A measure of how stiff a spring is.

What does a large spring constant mean?

The spring is stiff and requires more force to produce a given extension.

What does a small spring constant mean?

The spring is less stiff and requires less force to produce a given extension.