Motion

Speed

  • Speed is used to show how fast something is moving.


  • To calculate Speed, the formula: Speed = Distance / Time


  • The Value is displayed using Km/H, meaning kilometers travelled in one hour.

Graphs

Distance Over Time Graph:


  • Shows how long the time has taken to move a distance from one point.


  • Time on X axis, Distance on Y axis


  • Gradient of the graph line represents Velocity.

Velocity

  • Velocity is used to show how fast something in moving in one single direction.


  • Velocity is a vector quantity


  • The Value is displayed using m/s, meaning meters travelled in one second.

Velocity Over Time Graph:


  • Shows the velocity on something at a point in time.


  • You can calculate the distance travelled using the area underneath the graph.


  • The gradient of the graph line is the acceleration.

Acceleration

  • Acceleration is the the change in velocity.


  • The Value is displayed using m/s2, meaning meters travelled in one second squared.


  • Acceleration is calculated using the formula: a = v-u / t

Scalars and Vectors

A Scalar is a value with only magnitude

Scalar Examples:


  • Distance
  • Speed
  • Time
  • Energy
  • Volume
  • Mass

Vectors

A Vector is a quantity with both magnitude and direction

Vector Examples:


  • Displacement
  • Velocity
  • Acceleration
  • Force
  • Weight
  • Momentum

Resultant vectors are calculated by adding or subtracting vectors

Resultant Vectors:


  • If 2 Vectors are facing the same direction, The resultant Vector will be facing the same direction.


  • If 2 Vectors are facing different directions, The resultant Vector will be in the direction of the larger vector. If both vectors are equal. The resultant vector will be 0.

Forces

Types of Forces

Contact Forces:

  • Applied Force
  • Normal Force
  • Friction Force
  • Drag / Air Resistance

Non Contact Forces:

  • Gravitational Force

Mass and Weight

Mass:


  • All objects with mass exert a gravitational force, but the mass of people and objects is too small to have a significant gravitational force.
  • Objects with large mass will have a significant gravitational Force, such as planets and moons

Weight:


  • Weight is a force that is calculated using the formula w = m x g.


  • The unit of weight is N for Newtons

Resultant Forces

  • Resultant force is the net force acting on an object.


  • It is the sum of all the forces acting on the object at one time


  • Forces is a vector, it has both magnitude and direction. Some forces can be positive while others negative


  • If a 15 N force is pushing an object to the left, and a 10 N force is pushing the same object to the right, the resultant force will be a 5N force pushing the object to the left.

Newtons Laws

Newtons 1st Law:


A body will stay at rest, or stay moving at a constant velocity unless a resultant force acts on the body.

Newtons 2nd Law:


If a non-zero resultant force is applied to a body, then the body will accelerate.

Newtons 3rd Law:


If object A exerts a Force on Object B, then Object B will exert an equal force on object A, but in the opposite direction.

The Mechanic of Falling and centripetal force

The Mechanics of Falling:


When a body first starts falling, there is no significant amount of air resistance, the gravitational force is the only force accelerating it. As the body accelerates, air resistance starts to build, slowing down the acceleration. When the gravitational force and air resistance both become equal, that is when the body has reached terminal velocity, and will be falling at a constant speed.

Centripetal Force:


Centripetal Force is when an object is moving with a circular velocity because of 2 forces, one of the forces is behind the object, pushing it in the direction that keeps it spinning, while the other force pulls the object into a center point, making it spin in a circular direction.

Momentum:


Momentum is the force that carries on because of weight, an example would be: It is easier to stop a shopping trolley rolling towards you, than a train. This is because a train is way heavier, meaning it keeps it's momentum for longer and requires more force to stop it.

Turning Effect of Forces

Equilibrium:


An equilibrium is when an object experiences no rotational acceleration. An example would be a see-saw being completely balanced.

Turning effect of forces is when a force is applied at a distance to the fulcrum of an object used to apply force to an object. This allows the force to be more effective. Such as using a screwdriver to open a paint can.

Center of Mass:


The center of mass of an object is the point in the object that is the average of all mass in that object. It is the complete center of the objects weight.

Forces acting on Springs

How do forces act on springs:


  • Forces can compress springs ( Compressive Force )
  • Forces can stretch springs ( Tensile Force )
  • Forces can bend springs ( Bending Force )
  • Forces can twist springs ( Torsional Force )

Elastic Deformation:


Weight is applied to the spring. The spring will stretch. When the weight is removed the spring will return to it's original force.

Inelastic Deformation:


If the weight is too much for the spring to handle, the spring will stretch, but won't return to it's original force, it will be permanent deformed.