Physics Resultant Forces

Physics Resultant Forces

force=mass x acceleration

• A force is either a pull or a pull – they can be contact or non-contact forces and are measured in Newtons (N). 

  
  

• 1 Newton is the force required to accelerate a 1kg mass by 1m/s2 – which is where the above equation is derived. 

Modelling Forces

• •When we graphically represent forces we use arrows. 

• Remember that all force arrows start at the centre of mass. The bigger the arrow the bigger the force.

• Force is a VECTOR quantity, so the arrow shows the direction the force is acting in

  
  

Calculating resultant force

• Often many different forces will be acting on an object and these forces can be replaced by a single overall force – called the resultant force. 

Open Ended

What is the resultant force?

In which direction?

Open Ended

What is the resultant force?

In which direction?

Drawing free body diagrams

• Free body diagrams are diagrams used to show the relative magnitude (size) and direction of all the forces acting on an object in a given situation (they are vector diagrams).

• The length of the arrow represents the size of the force and has to be to scale

  The direction represents the direction the force is acting in. 

Free Body Diagram of a stationary duck

• Questions you need to ask

• 1.What forces are acting on the duck?

• 2.What direction are they acting in?

• 3.What are the sizes of these forces?

  
  

Answers

1.Gravity and upthrust

2.Gravity (down), Upthrust (up)

3.They have to be the same