Forces - Yr 8 Flashcards
What is a moment?
The turning effect of a force acting on an object, which causes the object to rotate around a pivot point
What two factors do moments depend on?
The distance from the pivot
The size of the force applied
What is a lever? What is it used for?
It is a tool that helps you to do a job more easily. Used to increase the turning effect of the force applied
What is the name of the force exerted?
Effort
What is the name of the force being moved?
Load
Why is it easier to open a door when you push it further from its hinges?
There is an increased distance between the force and hinges. For the same force, you have a larger moment so the door opens more easily
What is the equation to calculate a moment?
Moment (Nm/Ncm) = Force x Perpendicular distance
M = F x dp
State the principle of moments
Something is in equilibrium when the total clockwise moment is equal to the total anticlockwise moment
What is the centre of mass/gravity?
The point where the mass in an object is concentrated
How do you calculate a gradient?
Gradient = rise/run (change in y/change in x)
State Hooke’s Law
A material obeys Hooke’s Law is the extension of a spring is directionally proportional to the stretching force
How do you calculate the spring constant?
Force = Spring constant x Extension
F = k x e
Spring constant = Force/Extension
k = F/e
What is the spring constant of a spring that stretches by 5cm when a force of 8N is applied?
F = k x e | k = F/e
8 = k x 5 | k = 8/5
k = 1.6 N/cm
What does it mean if a material is below the elastic limit?
After stretching within the elastic limit, it returns to its original length (elastic behaviour)
What does it mean if a material is above the elastic limit?
Due to stretching beyond the elastic limit, it does not return to its original length, so the shape is permanently damaged (plastic behaviour)
