Chapter 4 forces in motion Flashcards
(16 cards)
What is the definition of weight?
Weight is the force due to gravity acting on a mass.
W=mg
What is the unit of force?
Newton (N)
What is the centre of mass?
The point at which the entire mass of an object can be considered to act.
What is a couple?
A pair of equal and opposite forces acting on a body but not along the same line, causing rotation.
What is torque?
The turning effect of a couple.
Torque = one of the forces × distance between them
Define moment of a force.
Moment = Force × perpendicular distance from pivot
τ=F×d
What is the principle of moments?
For a system in equilibrium, the sum of the clockwise moments equals the sum of the anticlockwise moments.
What are the two conditions for equilibrium?
Net force = 0
Net moment = 0
What is upthrust?
The upward buoyant force exerted by a fluid on a submerged or floating object.
What is Archimedes’ principle?
The upthrust on an object is equal to the weight of the fluid displaced.
What is pressure in a fluid?
Pressure = Force / Area
P=F/A
What is the equation for pressure at a depth in a fluid?
P=ρgh
Where:
ρ = density
g = gravity
h = depth
What is density?
Density = Mass / Volume
ρ=m/V
What is drag?
A resistive force that acts opposite to the direction of motion through a fluid.
How does drag affect terminal velocity?
Drag increases with speed until it balances weight, leading to zero acceleration (terminal velocity).
How does streamlining reduce drag?
By reducing turbulence and resistance, allowing smoother flow of fluid around the object.
