2 Velocity and acceleration
21 April 2023
Carriageways Cars Vans
Local roads
Single carriageway
Dual carriageway
Motorways
towing a trailer
Know your limit!What are the UK speed limits for cars and vans?
Vans between 2000kg and 7500kg.
2 Velocity and acceleration
21 April 2023
Carriageways Cars Vans
Local roads As marked As marked
Single carriageway roads
60 50
Dual carriageway roads 70 60
Motorways 70 * 70 *
towing a trailer * 60 * 60
Know your limit!Why do you think vans are
lower unless they weigh under 2000kg?
2 Velocity and acceleration• What is the difference between speed and
acceleration?• What is acceleration and what are its units?• What is deceleration?
21 April 2023
Motorways and dual carriageways have a central barrier and higher maximum speeds. Why is this safer than a single carriageway at 60mph?
World RecordsUsain Bolt is the 100m world record holder. Time = 9.58 seconds.
What was his average speed for this distance?
Speed =
Why was this the average speed?
What condition(s) would have to be met to make a valid record?
World RecordsUsain Bolt is the 100m world record holder. Time = 9.58 seconds.
What was his average speed for this distance?
Speed = distance = 100m = 10.44 m/s time 9.58s
Starts at zero and he takes time to reach his maximum speed.
Wind speed
Track distance
Timing system
Velocity = speed in a given direction
On a treadmill a speed is set. The belt runs at the speed set. E.g. 3 m/s
How fast is the runner running (speed)?
How quickly do they move in the direction they are running (velocity)?
Velocity tells us how quickly we are travelling in the direction we want to go.
DirectionVelocity tells us how quickly we are travelling in the direction we want to go.
If we wanted to travel from Nottingham to Donington the A52 is the most direct route.Distance = 48 miles.Time = 1 hour.
However, travelling due East is shorter: 40 miles.
What is the speed for this journey?
What is the velocity due East?
DirectionVelocity tells us how quickly we are travelling in the direction we want to go.
If we wanted to travel from Nottingham to Donington the A52 is the most direct route.Distance = 48 miles.Time = 1 hour.
However, travelling due East is shorter: 40 miles.
Average speed for this journey = 48 mph
Velocity due East = 40 mph East!
Movement in a circleIf an object moves in a circle at a constant speed of 10m/s what is its velocity?
A
B
C
D
Speed (m/s)
Velocity (m/s)
A 10
B
C +10
D 10 +
Movement in a circle
A
B
C
D
Speed (m/s)
Velocity (m/s)
A 10 -10
B 10 0
C 10 +10
D 10 0
+
Acceleration = Change in velocity per second
Acceleration = change in velocity (m/s)(m/s2) Time taken (s)
E.g. Rita Queen of speed accelerates from 0 to 30 m/s in 3 seconds. What is its acceleration in m/s2?
How can an object accelerate if its speed is constant?
Summary
• Velocity is speed in a given direction.• Acceleration is the change of velocity per
second.• An object travelling at a constant speed is
accelerating if its direction is changing.
Velocity = speed in a given direction
• On a trip across the Atlantic a plane takes 1 hour longer going west than going east.
• The air speed is the same for both trips. Why the difference?
New York London
7 hours
8 hours
Velocity = speed in a given direction
New York London
7 hours
8 hours
Air speed 540mph
Air speed 540mph
Wind 60mph
Velocity = 600mph
Wind 60mph
Velocity = 480mph