P2 - 5.3 Free Body Diagrams & Resultant Force Flashcards
What can we use free body diagrams to find
Resultant force
What is a free body diagram
All the forces acting on an object
In a free body diagram what do we use to show the direction of a force
Arrows
In a free body diagram was it the forwards arrow for
Thrust
In a free body diagram was it the backwards arrow for
Air resistance (drag)
In a free body diagram was it the downwards arrow for
Weight
In a free body diagram was it the upwards arrow for
Lift
Are free body diagrams vectors or scalars
Vectors because they must have a magnitude and direction
How can we see the direction of a vector in a free body diagram
The direction of the arrows
How can we see the magnitude of a vector in a free body diagram
How long the length of the arrows are (and labelled on arrow in newtons)
What is magnitude measured in
Newtons
When forces are acting in different directions what can happen
- some are going to cancel each other out
- this leaves the resultant force
What is meant by the resultant force
The overall force on an object
Scenario:
A plane has a lift of 80,000N and weight of 80,000N
What is the resultant force
80,000N (lift) - 80,000N (weight) = 0N
Resultant force = 0N
Scenario:
A plane has an air resistance of 90,000N and thrust of 120,000N
What is the resultant force
120,000N (thrust) - 90,000N (air resistance) = 40,000N
Resultant force = 30,000N in right direction
Scenario:
A plane has a lift of 80,000N and weight of 80,000N, an air resistance of 90,000N and thrust of 120,000N
What is the overall resultant force
80,000N (lift) - 80,000N (weight) = 0N
Resultant force = 0N
120,000N (thrust) - 90,000N (air resistance) = 40,000N
Resultant force = 30,000N in right direction
Overall force = 30,000N to the right
Scenario:
A plane has a lift of 80,000N and weight of 80,000N, an air resistance of 120,000N and thrust of 120,000N
What is the overall resultant force
80,000N (lift) - 80,000N (weight) = 0N
Resultant force = 0N
120,000N (thrust) - 120,000N (air resistance) = 0N
Resultant force = 0N in right direction
Overall force = 0N to the right
Object is perfectly balanced and in equilibrium
What is meant by equilibrium
There is no overall reactant force because everything is perfectly balanced
Forces acting in opposite directions on the same object can ‘cancel out’.
During take-off, a plane has a lift force (upwards force) of 690,000 N and a weight (downwards force) of 600,000 N.
What is the resultant force acting on the plane?
90,000N upwards
A resultant force acts upon an object.
Which two properties might be affected by that resultant force?
- Speed
- direction
What is meant by constant velocity
When all forces acting on an object are in equilibrium
