Forces and motion 2
Terms
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 Formula for speed

Speed (metres/second, m/s)
=
distance travelled (metres, m)

time taken (seconds, s)  Define speed
 The speed of an object describes the rate at which it is travelling
 Define velocity
 The velocitu of an object is both it's speed and direction
 Define acceleration
 The rate at whioch an objects velocity is changing
 Formula for acceleration

Acceleration (m/s²)
=
Change in velocity (m/s)

Time taken for change (s)  When acceleration and velocity are in the same direction does the object speed up or down
 Speeds up
 When acceleration and velocity are in opposite directions does the object speed up or down
 The object slows down
 the steeper the slope of a distance time graph, the greater the ......
 speed it represents.
 The steeper the slope of a velocity time graph the greater the .....
 acceleration it represents.
 The area under a velocity time graph represents what.
 The distance travelled.
 Newtons third law of motion states
 Whenever two objects exert forces on each other, the forces are equal in size and opposite in direction
 When forces cancel each other out we say they are ...
 balanced
 Do balanced forces affect an object's motion
 No
 Do unbalanced forces affect an object's motion
 Yes; depending on the direction of the unbalanced force it may cause the object to speed up, slow down or change direction
 The greater the size of the unbalanced force on an object the greater it's ...
 acceleration
 The bigger the mass of an object the ...... the unbalanced force that is needed to give it a particular acceleration
 larger
 Acceleration is proportional to ....
 force
 Newtons second law of motion

force
=
mass x acceleration  One newton will accelerate a mass of one kilogram at a rate of ....
 one metre per second²
 Frictional forces ten to make a moving object ....
 slow down
 What does the braking distance of a vehicle do if its speed increases
 The braking distance increases
 What are the two parts of a stopping distance

thinking
breaking  what is the breaking distance
 the distance the vehicle travels while the breaks are applied
 What is the reaction time
 Thinking distance  the time travelled by the vehicle in the time between the driver knowing the brakes should be applied and actually applying them
 Stopping distance =
 Thinking or reaction distance + braking distance
 Stopping distance increases if;

the road is wet or icy;
the driver is tried or under the influence of drink or drugs;
the vehicles brakes or tyres have been pororly maintained;
the vehicles spped before applying the brakes is greater  Weight =
 mass x gravitational field strength