Forces and motion

• Newtons 1st law is that an object will either remain stationary or moving at a constant speed if resultant force is zero.
• newtons 2nd law is that acceleration is directly proportional to the resultant force of an object. acceleration is inversely proportional to the mass of an object
• newtons 3rd law is that for every action there is an equal and opposite force being exerted on each other
• Distance is a scalar

  displacement is a vector
• typical values for:

  walking is 1.5m/s

  running is 3m/s

  cycling is 6m/s
• speed of sound= 330m/s
• speed is distance/time.
• difference between speed and velocity:

  -speed doesn’t have a direction

  -velocity is speed with a direction
• speed of an object on a distance time graph

  -gradient
• equation for acceleration= change in v/t
• acceleration from a velocity time graph

  -gradient
• distance travelled from a velocity time graph

  -area under graph
• v = final velocity

  u = initial velocity

  a = acceleration

  s = distance travelled
• if an object travels faster air resistance also increases
• terminal velocity occurs when the drag force is equal to the weight of the object, so the object is moving at its fastest speed
• stopping distance= thinking distance + braking distance

  -distance travelled during the drivers reaction time and the distance travelled under braking force
• typical reaction time= 0.2-0.9s
• factors that can affect a drivers reaction time:

  -fatigue

  -alcohol

  -drugs
• factors that can affect the breaking distance of a vehicle:

  -road conditions

  -quality of tires
• when force is applied to the breaks of a vehicle the kinetic energy in the car decreases and the heat of the breaks increase.
• if the braking force is larger there will be a larger deceleration.

  the bigger the deceleration the more likely the vehicle is to lose control.
• momentum = mass x velocity
• conservation of momentum is the total momentum of an object before an event is equal to the total momentum of the object after the event