Download OCR Biology Unit B2

OCR Physics Module P3 FORCES FOR TRANSPORT
P3a Speed
Speed
Increasing speed
Speed cameras
Distance-time graphs
Gradient
P3b Changing Speed
Speed-time graphs
Area under graph
Acceleration
Acceleration unit
Acceleration – speed-time graph
Acceleration – either
P3c Forces and Motion
Force and acceleration
Force, mass, acceleration
F, m and a
speed = distance ÷ time; unit is m/s (metres per second)
increases the distance travelled in the same time/reduces the time needed to cover the same distance
take two photographs: certain time apart; near marked lines on the road
straight line gradient (steady speed); steeper gradient (higher speed); horizontal line - stationary (zero speed)
calculate speed from gradient of graph [vertical axis change ÷ horizontal axis change]
horizontal line (constant speed); straight line positive [up] gradient (increasing speed); straight line negative
[down] gradient (decreasing speed); steeper gradient (more acceleration)
area under the line of a speed-time graph is the distance travelled
change in speed per unit time; acceleration = change in speed ÷ time taken
m/s2 (metres per second squared)
straight line gradient (constant acceleration); curved line (changing acceleration)
change in speed; change in direction
Forces – equal and opposite
(Total) stopping distance
Thinking distance
Thinking distance – factors
Braking distance
Braking distance – factors
Stopping distance – factors
Stopping distance – road safety
forces cause things to speed up or slow down
force (N) = mass (kg) X acceleration (m/s2); F = m x a
(constant mass) more force = more acceleration; (constant force) more mass = less acceleration; (constant
Acceleration) more mass = more force
when body A exerts a force on body B, body B exerts an equal but opposite force on body A
stopping distance = thinking distance [human reactions] + braking distance [car/road]
distance travelled between the need for braking occurring and the brakes starting to act
driver tiredness; drugs/alcohol; higher speed; distractions/lack of concentration
distance taken to stop once the brakes have been applied
road conditions (slippery/icy/wet); car conditions (bald tyres/poor brakes); more speed
friction; mass (load); speed; braking force
driving too close to car in front; speed limits; road conditions
P3d Work and Power
Work
Work – equation
Power
Power – equation
Cars
energy is needed to do work; work is done when a force moves an object; unit of work/energy is Joule (J)
work (J) = force (N) x distance (m); depends on size of the force (Newtons); distance (metres)
measurement of how quickly work is being done; measured in watts (W)
power (W) = work done (J) ÷ time (s)
power rating; fuel consumption; environmental issues; costs
P3e Energy on the move
Kinetic energy – KE
KE – equation
KE equation – application
Transport – fossil fuels
Transport – battery driven
Transport – solar powered
Joules (J); kinetic energy is greater for objects with: higher speed; greater mass
KE = ½ x mv2 [mass, kg; velocity, m/s]
relationship between braking distances and speed; everyday situations involving objects moving
petrol; diesel; cars pollute at the point of use
batteries need recharging; cars do not pollute at the point of use but power stations cause pollution
no pollution
P3f Crumple Zones
Safety features
Safety features – absorb energy
Safety features – reduce forces
Safety features – active
Safety features – passive
Crumple zones – force
Crumple zones – energy
Seatbelts – force
Seatbelts – energy
Anti-lock brakes
change shape; reduce injuries; absorb energy
heating in brakes; crumple zones; seat-belts; air bags
increasing stopping or collision time; increasing stopping or collision distance; decreasing acceleration
help reduce injuries; reduce chance of crash: ABS brakes; traction control
help reduce injuries; help avoid distractions; electric windows; cruise control; paddle shift
crumple in collision; changes shape; increase collision time; reduce acceleration; reduce force
crumple in collision; changes shape; absorbs KE
seatbelt stretches/increases in length; increase stopping distance; reduce acceleration; reduce force
seatbelt stretches/increases in length; absorbs KE
stops wheels locking; stops skidding; increases friction; keeps driver in control; reduces braking distance
P3g Falling Safely
Falling objects
Free-fall
Change forces
Terminal speed
Terminal speed – forces
Frictional forces
Air resistance
Streamlining
accelerate; weight pulls them towards centre of earth
constant acceleration due to gravity (g);
increase/decrease speed
objects falling through Earth’s atmosphere reach a terminal (constant) speed; balanced forces
higher speed = more drag; larger area = more drag; weight (driving force) = drag gives terminal speed
drag; friction; air resistance: act against movement; can be reduced (shape, lubricant)
drag; slows falling objects; parachutes; badminton shuttle-cock; not in outer space/Moon
wedge shape of sports car; deflectors on lorries and caravans; roof boxes on cars
P3h The energy of games and theme rides
Gravitational potential energy
objects have GPE because of mass and position in Earth’s gravitational field
GPE, mass and height
more mass = greater GPE; more height = greater GPE
GPE – equation
GPE (J) = mgh [mass (kg); g (usually 10 m/s2; h (m)]
GPE – different planets
GPE is also greater when the gravitational field strength (g) is higher – larger mass plant  higher value for g
Weigh
weight (N) = mass (kg) x gravitational field strength
Energy transfer
energy transfer between gravitational potential energy and kinetic energy – as objects fall/rise
At terminal speed
KE does not increase; GPE works against friction
Roller coaster – gravity ride
highest point = maximum GPE; lowest point = minimum GPE; changes of GPE  KE
Mass, speed and KE
KE = ½ x mv2; doubling mass doubles KE; doubling speed quadruples KE