Forces and motion

Speed
1. Formula speed=distance/time
2. Unit m/s
3. Velocity
  1. Speed of something and its direction of travel
  2. Velocity can be shown using an arrow ⟶
  3. Velocity is a quantatie that may have direction as well as magnitude and so it is called a vector
Accelaration
1. average acceleration=change in velocity/time taken
2. Unit m/s²
3. negative acceleration is called deceleration
4. Uniform acceleration means constant acceleration
Motion Graphs
1. Distance-time graphs
  1. Gradient of the line is numerically equal to the speed
    1. Gradient = y/x
  2. Different objects can show if the object is at a steady speed or stationary
  3. The graph can also show that the object is accelerating or deccelerating
2. Speed-time graphs
  1. Gradient of the line is equal to the acceleration
  2. Area under the line is equal to the distance travelled
3. Uniform and non-uniform acceleration
  1. Uniform
  2. Non-uniform
Free fall
1. Unit g
  1. On earth 10m/s²
  2. g decreases as the object is moved away from each
2. Acceleration of free fall- Same for all objects falling near the earth's surface, either light or heavy
3. When throwing a ball at the air...
  1. Upward velocity of 30m/s is equal to downward velocity of -30m/s
  2. Whatever the ball is travelling up or down it is gaining downward velocity at the rate of 10m/s (g)
Forces in balance
1. Force
  1. Unit Newton(N)
  2. Small forces can be measured using a spring balance. The greater the force the more the spring is stretched and higher it is the reading on the scale
  3. Examples of different forces
    1. Tension
    2. Upthrust
    3. Weight
    4. Friction
    5. Air resistance
  4. If many forces in an object are in balance, they cancel each other out
    1. With balanced forces on it, an object is either at rest, or moving at a steady velocity
  5. Terminal velocity
    1. Example: a skydiver falling from a hovering helicopter
      1. As her speed increases, the air resistance on her also increases. Eventually, it is enough to balance her weight, and she gains no more speed. She is than at her terminal velocity.
2. Newton's first law of motion (if no external force is acting on it the object will)
  1. if stationary, remain stationary
  2. if moving, keep moving at a steady speed in a straight line
Force, mass and acceleration
1. Inertia
  1. Resistance to a change in velocity or direction
  2. The more mass something has, the more inertia it has
2. Resultant force
  1. When two forces are unbalanced. Together, they are equivalent to a single force. This is called the resultant force
  2. Resultant force is equal to zero when forces are balanced, and there is no acceleration
3. Resultant force= mass x acceleration
  1. F=ma
  2. Newton's second law of motion
Force, weight and gravity
1. Gravitattional force
  1. All masses attract each other
  2. The greater the masses, the stronger the force
  3. The closer the masses, the stronger the force
  4. Gravitational field strength (g)
    1. Region in which a mass experiences a force due to gravitational attraction
    2. weight= mass x g
      1. w=mg
2. Weight
  1. Measured in newtons
  2. Near the earth's surface, an object of mass 1 kg has a weight of 9.8 N
  3. Weight can change from place to place, but mass remains the same

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Forces and motion

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