Motion and Forces

What is a scalar quantity?;A quantity with magnitude (size) but no specific direction.

What is a vector quantity?;A quantity with both magnitude (size) and a specific direction.

What is the difference between scalar and vector quantities?;Scalars have magnitude only, whereas vectors have both magnitude and direction.

Which of these are scalar quantities: distance, speed, acceleration, force, mass, momentum and energy?;Distance, speed, mass and energy are scalars.

Which of these are vector quantities: displacement, velocity, acceleration, force, weight and momentum?;Displacement, velocity, acceleration, force, weight and momentum are vectors.

What is velocity?;Speed in a stated direction.

What is the equation for average speed?;Average speed = distance ÷ time.

What is the equation for distance travelled?;Distance = average speed × time.

What is the unit of speed?;Metres per second (m/s).

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

How do you determine speed from a distance-time graph?;Calculate the gradient: speed = change in distance ÷ change in time.

What does a horizontal section on a distance-time graph represent?;The object is stationary because its distance is not changing with time.

What does a steeper gradient on a distance-time graph mean?;A greater speed.

What is the equation for acceleration?;Acceleration = change in velocity ÷ time taken.

What is the equation for acceleration using initial and final velocity?;a = (v − u) ÷ t.

What do the symbols in a = (v − u) ÷ t represent?;a = acceleration, v = final velocity, u = initial velocity, t = time.

What is the unit of acceleration?;Metres per second squared (m/s²).

What equation links final velocity, initial velocity, acceleration and distance?;v² − u² = 2ax.

What do the symbols in v² − u² = 2ax represent?;v = final velocity, u = initial velocity, a = acceleration and x = distance.

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

How can acceleration be calculated from a velocity-time graph?;Calculate the gradient: acceleration = change in velocity ÷ change in time.

How can distance travelled be determined from a velocity-time graph?;Calculate the area between the graph line and the time axis.

What does a horizontal section on a velocity-time graph represent?;Constant velocity.

What does an upward slope on a velocity-time graph represent?;Positive acceleration.

What does a downward slope on a velocity-time graph represent?;Deceleration (negative acceleration).

What is a light gate used for?;Measuring the speed of an object as it passes through a beam of light.

What are typical everyday speeds?;You should know approximate speeds for wind, sound, walking, running, cycling and transport systems.

What is the acceleration due to gravity, g, near Earth's surface?;Approximately 10 m/s².

What is Newton's first law?;If the resultant force on an object is zero, it remains at rest or continues moving at constant velocity. If the resultant force is not zero, its speed and/or direction changes.

What happens when the resultant force on an object is zero?;The object is either stationary or moves at constant velocity.

What happens when the resultant force on an object is not zero?;The object's speed and/or direction changes, meaning it accelerates.

What is Newton's second law?;Resultant force = mass × acceleration (F = ma).

What is the unit of force?;Newton (N).

What is the equation for force?;F = ma.

What is weight?;The force acting on an object due to gravity.

What is the equation for weight?;W = mg.

What are the units in W = mg?;W is in newtons (N), m is in kilograms (kg), and g is in newtons per kilogram (N/kg).

How is weight measured?;Using a force meter (newton meter), which measures the force acting on the object.

What is the relationship between weight and gravitational field strength?;Weight is directly proportional to gravitational field strength for a given mass: W = mg.

What happens to weight if gravitational field strength increases?;Weight increases proportionally, provided mass stays constant.

What happens to mass when an object is moved to a different planet?;Its mass stays the same.

What happens to weight when an object is moved to a different planet?;Its weight changes because gravitational field strength is different.

What is investigated in the core practical on force, mass and acceleration?;The relationship between force, mass and acceleration by varying the masses added to trolleys.

What happens to acceleration when the resultant force increases while mass stays constant?;Acceleration increases.

What happens to acceleration when mass increases while resultant force stays constant?;Acceleration decreases.

What happens to velocity when an object moves around a circle at constant speed?;Its velocity changes because its direction is continuously changing.

Why is circular motion an example of acceleration even at constant speed?;Because velocity is a vector and its direction changes.

What is centripetal force?;The resultant force acting towards the centre of a circular path that keeps an object moving in a circle.

In which direction does centripetal force act?;Towards the centre of the circle.

What is inertial mass?;A measure of how difficult it is to change an object's velocity, including bringing it from rest.

How is inertial mass defined?;Inertial mass = force ÷ acceleration.

What is Newton's third law?;When two objects interact, they exert equal and opposite forces on each other.

Where do Newton's third-law force pairs act?;On different objects.

How does Newton's third law apply to collisions?;Each object exerts an equal and opposite force on the other during the collision.

What is momentum?;The product of an object's mass and velocity.

What is the equation for momentum?;p = mv.

What is the unit of momentum?;Kilogram metre per second (kg m/s).

What happens to the total momentum in a collision in a closed system?;Total momentum is conserved.

How can momentum be used to analyse collisions?;The total momentum before a collision equals the total momentum after the collision, allowing unknown velocities or masses to be calculated.

What is the equation linking force and change in momentum?;F = change in momentum ÷ time.

What is the equation for force using momentum?;F = (mv − mu) ÷ t.

What do the symbols in F = (mv − mu) ÷ t represent?;F = force, m = mass, v = final velocity, u = initial velocity and t = time.

How can human reaction time be measured?;For example, using a ruler-drop test or an electronic reaction-time apparatus.

What is a typical human reaction time?;Approximately 0.2–0.3 seconds, although it varies between individuals and circumstances.

What is stopping distance?;The total distance travelled by a vehicle from noticing a hazard to coming to a complete stop.

What is the equation for stopping distance?;Stopping distance = thinking distance + braking distance.

What is thinking distance?;The distance travelled while the driver reacts to a hazard.

What is braking distance?;The distance travelled after the brakes are applied until the vehicle stops.

What factors affect stopping distance?;Vehicle mass, vehicle speed, driver's reaction time, condition of the brakes, condition of the road and friction between tyres and the road.

How does increased vehicle speed affect stopping distance?;It increases both thinking distance and braking distance.

How does increased vehicle mass affect stopping distance?;It generally increases the braking force and energy that must be dissipated, making stopping more difficult.

How does increased driver reaction time affect stopping distance?;It increases thinking distance.

How do drugs and distractions affect reaction time?;They can increase reaction time, increasing thinking distance and therefore stopping distance.

How does poor road condition affect stopping distance?;Reduced friction can increase braking distance.

How does poor brake condition affect stopping distance?;It can increase braking distance.

Why are large decelerations dangerous?;They produce large forces on passengers and objects, which can cause serious injury.

How can the force during a large deceleration be estimated?;Use F = ma, where a is the deceleration.

How does emergency stopping distance vary with speed?;Stopping distance increases as speed increases, with braking distance increasing approximately with the square of speed.

How is braking distance related to initial velocity?;Braking distance is proportional to initial velocity squared, assuming other factors remain constant.

Why is braking distance proportional to velocity squared?;The work done to bring the vehicle to rest equals its initial kinetic energy, and kinetic energy is proportional to velocity squared.

What is the relationship between work done during braking and kinetic energy?;The work done to bring a vehicle to rest is equal to its initial kinetic energy.