Physics 2.2

Physics 2.2

1. Forces between objects

   • Forces are measured in newtons
   • Objects always exert equal and opposite forces on eachover
     • Action and reaction forces
   • A force can change the: shape,motion or state of rest

2. Resultant force

   • The resultant force is a single force that has the same effect as all forces acting on object
   • If an object is accelerating there must be a resultant force acting on it
     • Accelerating can be speeding up,slowing down or changing direction

3. Force and acceleration

   • Resultant force=mass x acceleration
   • The bigger the resultant force- the greater its acceleration
   • Greater the mass- smaller acceleration

4. On the road

   • Friction and air resistance oppose the driving force of the car
   • Stopping distance=time it travels during reaction time+ breaking time
   • Thinking distance is increased if driver is tired or drunk
   • Braking distance can be increased by condition of car and road

5. Falling objects

   • The weight of an object is the force of gravity on it
   • The terminal velocity of a falling object is the velocity when falling in a fluid
     • The weight is then equal to the drag force on the object

6. Stretching and squashing

   • The extension is the difference between the length of the spring and its original length
   • the extension is directly proportional to the force applied to it
     • If we apply too big of a force we have exceeded the limit of proportionality

7. Force and speed issues

   • Fuel economy- reducing speed reduces amount of fuel
   • Anti-skid surfaces increase friction preventing skids