Forces in action Flashcards
Everything you need to know to get A* in OCR Physics A Level, closely following the specification and the textbook
What is equation for net force?
F=ma
What is the unit of force?
Newton
What is the equation for the weight of an object?
W=mg
Define tension
The pulling force exerted by a string, cable or chain on an object
Define normal contact force
The force exerted by a surface on an object, which acts perpendicularly to the surface
Define upthrust
The upwards buoyant force exerted on a body immersed in fluid
Define friction
The force arising when two surfaces rub against each other
Define drag
The frictional force experienced by an object travelling through fluid
What are the 2 factors that affect drag?
The speed of the object and its cross-sectional area
Define terminal velocity
The constant speed reached by an object when the drag force (upthrust) is equal and opposite to the weight of the object
What is the equation for the moment of force?
moment = Fx
Define a couple
A pair of equal and opposite forces acting on a body but not in the same straight line
Define a torque
The moment of a couple
What is the equation for the torque of a couple
Fd
What is the principle of moments?
For a body in rotational equilibrium, the sum of the anticlockwise moments about any point is equal to the sum of the clockwise moments about that same point
Define the centre of mass
A point through which any externally applied force produces a straight line motion but no rotation
Define the centre of gravity
An imaginary point at which the entire weight of an object appears to act
Define equilibrium
When the net force acting on a body is 0
What is the equation for denisty?
ρ = m/V
What is the equation for pressure?
P=F/A
What is the equation for pressure in fluids?
p = hρg
What is the equation for upthrust?
upthrust = Axρg
Where A = cross sectional area
x = displacement
What is Archimedes principle?
The upthrust on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of fluid that body displaces
