Physics - Y10: Forces, Motion and Momentum

What is a scalar quantity?

A quantity that has only magnitude and no direction (e.g. temperature, mass)

What is a vector quantity?

a quantity that has both magnitude and direction (e.g. momentum, velocity, weight)

How do force arrows represent forces?

Direction = direction of force.

Length= size of force

What is a resultant force?

The force left over when forces acting in opposite directions are cancelled out.

How do you calculate the resultant force?

Subtract the total force in one direction from the total force in the other direction.

What is the resultant force when an object is balanced?

0N

What is Newton's first law of motion?

An object will move at the same speed and direction unless it experiences a resultant force.

What are the effects of a resultant force?

Acceleration - speeding up, slowing down, changing direction.

What is mass?

The quantity of matter in an object (Units = kg)

What is weight?

A force caused by gravity pulling downward on an object (units = N)

What is a force meter?

An instrument for measuring forces.

What is gravitational field strength?

The strength of gravity, which is different of different planets (units = N/kg)

What is the equation for weight?

Mass x gravitational field strength

What is air resistance

A force created by the air pushing against you as you move. Faster movement = greater air resistance.

What is motion like whilst falling?

Accelerate until air resistance is equal to the weight. Now there is no resultant force so speed stays constant.

What is Newton's second law of motion?

Force = mass x acceleration

When is acceleration greatest?

When the force is greater or the mass is smaller.

How do you calculate the acceleration?

mass/force (units = m/s^2)

What is Newton's third law?

For every action there is an equal and opposite reaction (if the same size and acting in opposite direction)

What is momentum?

The tendency of an object to keep moving.

What is the equation for momentum?

momentum = mass x velocity

(unit = kgm/s)

What is the equation for force in relation to momentum?

Force = change in momentum/time)

What is the conservation of momentum?

Total momentum before and after a collision is the same.

What is a stopping distance?

The distance travelled from when a hazard is seen to when you fully stop.

What is thinking distance?

The distance travelled from when a hazard is seen to when you brake.

What is braking distance?

The distance travelled from when you brake to when you fully stop.

How do you calculate the stopping distance?

Thinking distance + braking distance

Why might the thinking distance by increased?

Higher speed, tiredness, illness, drugs, distractions, old age

Why might the braking distance be increased?

Higher speed, poor brakes, poor tyres, wet/icy/gravelly road, downhill, heavier load

What is the equation for speed?

speed = distance/time

What is the definition of acceleration?

rate of change of velocity

What is the equation that links velocity with acceleration and distance?

ending velocity^2 - starting velocity^2 = 2 x acceleration x distance

(v^2 - u^2 = 2as)

What is displacement?

The shortest straight-line distance from an object's initial position to its final position.

How do you work out the speed on a distance-time graph?

By finding the gradient of the line.

How do you find the distance travelled on a velocity-time graph?

The area beneath the line.

How do you calculate the thinking distance?

speed x reaction time

How do you calculate the braking distance?

velocity^2 / 2 x acceleration

Calculate the relationship between a force and extension of a spring?

As force increases, the extension increases.

What is Hooke's law?

Force is proportional to extension so long as the elastic limit is not exceeded.

What is the equation for a force on a spring?

Force = spring constant x extension

Describe an experiment to investigate the relationship between force and extension.

-Clamp stand to table

-Hang spring from top of stand

-Attack ruler with clamp to stand where zero is at the same height as top of spring

-Adjust ruler to vertical

-Measure the unstretched spring

-Add 1.0N to spring and measure length of spring

-Repeat adding more weight

-extension = length with added weight - length with no weight.