Topic 9- Forces and their effects Flashcards
How can objects interect?
-Non contact fields
-Contact forces
What is a non contact force?
-Occurs in a field
-Objects are not physically touching
-E.g gravitational or electrostatic or magnetic
What are contact forces and what are two types?
-Physically touch:
-Normal contact force at 90 degrees
-Friction
Where does the reaction force act?
Perpendicular to the surface (90 degrees)
Which way does friction act?
Opposite to the direction
Vector vs Scalar
-Both magnitude
-Vector has direction
Vector examples? x5
-Displacement
-Velocity
-Force
-Acceloratiton
-Momentum
Scalar examples? x5
-Energy
-Speed
-Disance
-Mass
-Temperature
VECTOR DIAGRAMS? what are they?
-Draw all forces on eachother from new direction + proportional length
-Draw final line (start to finish)= resultant force
-Find angle of resultant force to first movement
What do resultant forces have? on a vector diagram?
horizontal + verticle componenants
What does a free body diagram show?
-All the forces that are acting on an object
-Using force angles (diff sizes)
What are the 4 arrows ona free body diagram called?
-Lift vs Weight
-Thrust vs Drag
What if resultant force is 0?
-Balanced, at equilibrium
-Will no longer accelerate
-Will contue its movement
When do forces cuase rotation?
-When there is a moment or pivot
-E.g child on a seewsaw or using a hammer
What is a moment?
The turning effect of a force around a pivot
How do we work out the moment?
Force x perpendicular distance (from the moment to force)
What is the principial of moments?
-Sum of clockwise vs anticlockwise moment
When is the moment at equilibrium?
anticlockwise moment= clockwise moment
What does a lever do?
-Transmits the turning effect of a force
e.g we apply an input force, it applies an output force
If input and output force are on opposite sides of the pivot what happens?
Act in different directions e.g scissors
If input and output force are on the same sides of the pivot what happens?
Act in the same direction
How does the lever cuase a larger force?
-Allows effort to be further from pivot
- e.g transmits force for distance
What does a gear do?
Transmits the turning effects
e.g the gears allows the turning effect of the engine to be transmitted to the wheel
What happens if gears are interlocking?
-cuases the other gear to move
-In the opposite direction
How do different radius’ effect the gears rotation?
-A larger radius means a larger turning effect
-Other gears will rotate in proportion to their radius e.g 2x smaller gear will rotate twice for every one rotation of the bigger gear
What is the difference workdone of two gears with different radius’?
-The same
-One rotates more but has a smaller turning effect
-Other rotates less but has a larger turning effect
How to reduce unwanted energy loss?
Lubrication reduces friction and therefore reduces heat loss and increases efficiency
What is the fuclrum?
A pivot
What is the first class lever?
-The fulcrum (pivot) is in the middle
e.g seesaw
between load and effort
What is the second class lever?
-The load is in the middle
e.g wheelbarrow
between fulcrum and effort
What is the third class lever?
-The effort (force) is in the middle
-e.g tweezers
Between load and fulcrum
