Physics Y11 Topic 1

What is a physical quantity?

A measurable property of a phenomenon, object, or substance expressed with a number and a unit.

What is a unit?

A defined standard used to measure a physical quantity.

Why is the SI system used in science?

It provides a universal measurement system so results can be compared worldwide.

What is the SI base unit of length?

metre (m)

What is the SI base unit of mass?

kilogram (kg)

What is the SI base unit of time?

second (s)

What is resolution in measurement?

The smallest change in a quantity an instrument can measure.

What is accuracy?

How close a measured value is to the true value.

What is precision?

How close repeated measurements are to each other.

Why repeat measurements in experiments?

To reduce random errors and improve reliability.

What instrument measures very small thickness accurately?

A micrometer screw gauge.

What is density?

Mass per unit volume.

What is the formula for density?

ρ = m / V

What is the SI unit of density?

kg m⁻³

What is mass?

The amount of matter in an object and a measure of its inertia.

What is speed?

The rate of change of distance with time.

What is the formula for speed?

v = d / t

What is the SI unit of speed?

metres per second (m/s)

What is velocity?

The rate of change of displacement with time including direction.

What is acceleration?

The rate of change of velocity with time.

What is the formula for acceleration?

a = Δv / t

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 the gradient of a velocity–time graph represent?

Acceleration

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

Displacement

What is a force?

A push or pull that can change the motion of an object.

What is the SI unit of force?

Newton (N)

What is the resultant force?

A single force equivalent to all forces acting on an object.

What does Newton’s Second Law state?

The resultant force on an object equals its mass multiplied by its acceleration.

What is the formula for Newton’s Second Law?

F = ma

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

Acceleration increases.

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

Acceleration decreases.

What is the difference between mass and weight?

Mass is the amount of matter (kg) while weight is the gravitational force acting on that mass (N).

Does mass change on different planets?

No.

Does weight change on different planets?

Yes because gravitational field strength changes.

What is Hooke’s Law?

The extension of a spring is directly proportional to the applied force provided the elastic limit is not exceeded.

What is the formula for Hooke’s Law?

F = kx

What does k represent in Hooke’s Law?

The spring constant which measures stiffness.

What does x represent in Hooke’s Law?

The extension from the spring’s natural length.

What is the elastic limit?

The point beyond which a material will not return to its original shape.

What does the gradient of a force–extension graph represent?

The spring constant.

What happens if a spring is stretched beyond the elastic limit?

It becomes permanently stretched.

What is momentum?

The quantity of motion equal to mass multiplied by velocity.

What is the formula for momentum?

p = mv

What is the SI unit of momentum?

kg m s⁻¹

What is the law of conservation of momentum?

In a closed system with no external forces total momentum before a collision equals total momentum after the collision.

Why is momentum a vector quantity?

It has both magnitude and direction.

What is impulse?

The change in momentum caused by a force acting over time.

What is the formula for impulse ( involving time )?

J = Ft

How is impulse related to momentum change?

J = Δp = pfinal − pinitial

What is the SI unit of impulse?

Newton seconds (N·s).

Why do airbags reduce injury in crashes?

They increase the time of impact reducing the force for the same momentum change.

A 3.0 kg cart moves at 5.0 m/s. What is its momentum?

15 kg m s⁻¹

A 0.20 kg ball moving at 12 m/s is caught and brought to rest in 0.25 s. What average force acts on the ball ( use negative number )?

−9.6 N

A spring with spring constant 250 N/m is stretched 0.040 m. What force is applied?

10 N

A force of 18 N acts on a 6 kg object. What acceleration occurs?

3 m/s²

A 0.50 kg ball moves at 8 m/s then rebounds at 6 m/s in the opposite direction. What is the change in momentum?

−7 kg m s⁻¹

A constant force of 40 N acts for 0.30 s. What impulse is applied?

12 N·s

A 2 kg trolley moving at 3 m/s collides with a stationary 4 kg trolley and they stick together. What is their final velocity?

1 m/s

A spring stretches 0.020 m under a 4 N force. What is the spring constant?

200 N/m

A 1.5 kg object speeds up from 2 m/s to 10 m/s in 4 s. What average force acts on it?

3 N

A 0.15 kg baseball moving at 20 m/s is hit back at 35 m/s in the opposite direction in 0.005 s. What average force acted on it ( use negative number )?

−1650 N