Topic 9 - Forces and their effects Flashcards
Describe how objects can interact at a distance without contact, linking it to gravitational fields
In gravitational attraction there is an attraction between two objects with mass, the larger mass gives greater attraction
Describe how objects can interact at a distance without contact, linking it to electrostatic fields
In electrostatic attraction/repulsion a larger charge gives greater force.
Like charges repel, opposite charges attract.
Describe how objects can interact at a distance without contact, linking it to magnetic fields
In magnetic attraction/repulsion a stronger magnet gives a stronger field, having a greater force.
Like poles repel, opposite poles attract.
What is Newton’s third law?
Every action has an equal or opposite reaction
Action-reaction pairs must be…
-Be opposite in direction.
-Be the same size.
-Be the same type.
(i.e both non-contact magnetic forces)
-Act on opposite objects.
Describe how objects can interact by contact, linking it to normal contact force
The force is perpendicular to the plane of contact
Describe how objects can interact by contact, linking it to friction
Surfaces that are rough cause friction when moved
Explain the difference between vector and scalar quantities using examples
-Scalar just has size e.g. mass, distance, speed, etc.
-A vector has size and direction e.g. weight, velocity, force, displacement, etc.
How do you draw a vector diagram and calculate the resultant force?
https://www.youtube.com/watch?v=PG8wV022Eu0
What are the key points on free body diagrams?
-Forces acting on one object.
-Object can be simplified to a point.
-Weight always acts vertically down.
-Normal/reaction force always acts at 90° to the surface.
-Friction acts in the opposite direction to movement, along line of contact
In scale drawings:
-The length of each arrow represents its size (in relation to the other forces acting on the object)
-If arrows are in opposite directions with equal length the forces cancel out so the object is in equilibrium so travels at a constant velocity (This could be continues moving with no acceleration or doesn’t move)
What do isolated solid systems mean?
Isolated systems do not allow the transfer of matter or energy to or from its surroundings.
e.g. if a magnetic ball is rolling down a hill a magnet at the top of the hill would be an external force
When does rotation occur?
-If an object is attached is attached to a pivot point
-And a force is applied NOT towards the pivot point
-If the force is applied perpendicular to the object it will move about the pivot in this direction.
-If the force is applied not perpendicular to the object you need to find perpendicular distance from pivot to line of force to see which direction it will turn
https://pmt.physicsandmathstutor.com/download/Physics/GCSE/Notes/Edexcel/9-Forces-and-their-Effects/Summary%20Notes.pdf
What is the equation for moment of a force?
moment of a force (newton metre, N m) = force (newton, N) × distance normal to the direction of the force (metre, m)
When does equilibrium occur for rotational forces?
the sum of clockwise moments = the sum of anti-clockwise moments
