P5b Motion

What is meant by a vector quantity?

a quantity with magnitude and direction

What is meant by a scalar quantity?

a quantity with magnitude only

What is the difference between distance and displacement?

Distance measures magnitude (scalar) while displacement measures magnitude and states direction (vector)

What is an average human walking speed?

around 1.5 m/s

What is velocity?

how fast something travels in a specific direction

What is the difference between speed and velocity?

Velocity measures magnitude and direction (vector) while speed only measures magnitude (scalar)

What is an average human running speed?

around 3 m/s

What is an average human cycling speed?

around 6 m/s

What is an average value for the speed of sound in air?

around 330 m/s

How can you find the speed of an object from a distance-time graph?

calculating the gradient

What is acceleration?

how quickly an object changes its velocity

What equation is used to calculate acceleration?

acceleration = change in velocity / time

What does 'decelerating' mean?

an object is changing its speed by slowing down

How can you find the acceleration of an object from a velocity-time graph?

by calculating the gradient

What is Newton's 1st law?

If the resultant force on an object is zero, its motion does not change

What is Newton's 2nd law?

An object's acceleration is directly proportional to the resultant force acting on it, and inversely proportional to its mass

What does the symbol ~ mean?

approximately

What is Newton's 3rd law?

Whenever two objects interact they will exert equal and opposite forces on each other

What is stopping distance?

the distance a vehicle travels during the driver thinking and the driver braking

What is a typical human reaction time?

0.2 - 0.9 seconds

What factors affect a driver's reaction time?

Tiredness, drugs, alcohol and distractions.

What factors affect braking distance?

poor road conditions (wet or icy), poor weather conditions, poor vehicle conditions (brakes or tyres)

Why is applying the brake too hard/quickly dangerous?

Very large decelerations may cause brakes to overheat or loss of control of the vehicle