4 - Forces in Action Flashcards
Energy transfers examples
heating (thermal), electrical, light, sound, kinetic forces (mechanical work), nuclear (radiation)
Energy stores examples
gravitational potential, chemical potential, thermal store, elastic potential, nuclear potential, magnetic potential, kinetic store
Contact forces
air resistance, friction, upthrust, tension, compression, thrust
Non-contact forces
weight, electrostatic, magnetic
4 Fundamental forces
gravitational (acts on anything with mass e.g. protons, neutrons, electrons), electrostatic/electromagnetic, (acts on anything with charge e.g. protons, electrons), weak nuclear, strong nuclear
If resultant force acting on an object is 0…
object is stationary or remains at constant speed as forces are balanced
Centre of mass
The point at which an object’s mass is centred or concentrated, the point through which a single force on the body has no turning effect. For regular symmetrical objects, the COM is the centre of the object
Centre of gravity
Weight is caused by the attraction of every atom inside an object to every atom inside the Earth. The sum of all of these forces appear to act from a single point for any object, this is the centre of gravity
How to find COM for irregular objects
First, make a hole in the material and hang. Hang a piece of string from it with a weight on the end so you can trace the line (plumb line). Make another hole in a different place and do the same thing. Where the lines cross is the centre of mass for that object
What factors affect stability
width of base and height of centre of mass. More stable objects have wide bases and low COMs
What is a moment?
the turning effect of a force and will act around a pivot. A moment can act clockwise or anticlockwise
Moment equation
Moment = Fd
Moment (Nm) = Force (N) x perpendicular distance to the line of action of the force (m)
If a body is in equilbrium…
turning force resultant force is 0, the sum of the clockwise moments is equal to the sum of the anti-clockwise moments (CW=ACW
Stable equilibrium:
If a body is displaced from the equilibrium position then released, it will return to the equilibrium position
Unstable equilibrium:
If a body is displaced from the equilibrium position then released, it will not return to the equilibrium position.