4.5 moments and equilibrium Flashcards
For an object resting/moving along an inclined plane, which direction do we resolve forces at?
parallel and perpendicular to plane
How do you calculate the moment of a force?
moment = force x perpendicular distance from the pivot
State the 2 conditions for an object to be in equilibrium
net force on the object must be zero and the net moment on the object must be zero
State the principle of moments
for an object to be in equilibrium the sum of the clockwise moments must be equal to the sum of the anticlockwise moments exerted on it
what is the name for a string with a weight used to provide a vertical reference line
a plumb line = a weight attached to a string used as a vertical reference line to ensure a structure is centered
what is the formula for density
density = mass / volume
define pressure
pressure = force / area - the force exerted per unit cross-sectional area, measures in pascals (Pa)
explain why a skydiver reaches terminal velocity
- as their velocity increases, the drag force acting on them also increases
- until the drag force acting on them is the same as their weight
- this causes the net force on them to be zero
- therefore, they no longer accelerate, as both forces acting on the are equal to each other
define torque (of a couple)
the product of one of the forces of a couple and the perpendicular distances between the forces - one of the forces x perpendicular separation between the forces
define a couple
a pair of equal and opposite forces acting on a body but not in/on the same straight line
define torque
the moment of a couple
Why does any force that acts through a chosen pivot doesn’t cause a moment about that pivot
Because the perpendicular distance from the force acting through that point to the pivot is zero
Define equilibrium
A body is in equilibrium when the net force and net moment acting on it are zero
