Transcript Forces and Motion - science

Forces and Motion
Objectives: To review
Speed
Distance-Time Graphs
Velocity-Time Graphs
Acceleration
Newton’s Laws
Falling Objects
Forces on vehicles
Speed
• Equation
Displacement – Time Graph
• Distance is how far you go.
• Displacement is how far you are from a
particular place.
Displacement-Time and
Velocity-Time Graphs
• Drawing graphs (gradient and area)
Acceleration
• Acceleration is the change in velocity
over a given time.
acceleration = Change in speed = (final speed – initial speed)
Change in time
(final time – initial time)
Forces
• Newton’s First Law.
An object will remain stationary or go
at a constant velocity unless there is
a resultant force on it. This will make
it change direction or change its
speed.
Forces
• Newton’s Third Law
• Whenever you push something, it
pushes back with the same type of
force exactly the same amount.
• (Every force has an equal and
opposite reaction force)
Forces
• Newton’s Second Law
• The acceleration of something is
proportional to the amount of force on it
and inversely proportional to its mass
•
• OR
•
• Force = mass x acceleration
Pushing things
Graphs
Falling Objects
• Drop stuff
Stopping Distance
• This is the distance moved by the vehicle
between the driver seeing the obstacle
and the vehicle stopping.
• The vehicle keeps moving at a steady
speed whilst the driver reacts
(thinking distance)
• The vehicle slows down whilst the brakes
are applied
(braking distance)
• Stopping = Thinking + Braking
Stopping Distance
Total stopping
distance is the area
under the whole
graph
Speed
(m/s)
Thinking distance
Braking distance
Reaction time
Time (s)
Thinking Distance
Factors that affect thinking distance are:
• driver tiredness;
• influence of alcohol or other drugs;
• more speed;
• distractions or lack of concentration.
Braking distance:
Factors that affect braking distance are:
• road conditions – slippy, icy, wet;
• car conditions - bald tyres, poor brakes;
• more speed.