Derivation of ?p = ρg?h Hydrostatic pressure?is the pressure that is exerted by a?fluid?at equilibrium at a given point within the fluid, due to the force of gravity The derivation for this equatio...
Pressure Pressure tells us how concentrated a force is, it is defined as the?force per unit area Pressure is equal to the force per unit area This equation tells us If a force is spread over a larg...
Density Density is the?mass per unit volume?of an object Objects made from low-density materials typically have a lower mass For example, a balloon is less dense than a small bar of lead despite oc...
Equilibrium A system is in equilibrium when all the forces are balanced. This means: There is?no?resultant force There is?no?resultant torque An object in equilibrium will therefore remain at rest,...
Couples A couple is a?pair?of forces that acts to produce?rotation?only Unlike moments of a single force, the moment of a couple doesn’t depend on a pivot, only on the perpendicular distance betwee...
What is a Moment? A moment is the?turning effect of a force Moments occur when forces cause objects to?rotate?about some pivot The moment of a force is given by Moment (N m) = Force (N) × perpendic...
Centre of Gravity The centre of gravity of an object is?the point at which the weight of the object may be considered to act For example, for a person standing upright, their centre of gravity is r...
Elastic Collisions When two objects collide, they may spring apart retaining all of their kinetic energy. This is a perfect elastic collision An elastic collision is one where?kinetic energy is con...
The Principle of Conservation of Momentum The principle of conservation of momentum is: The total momentum of a system remains constant provided no external force acts on it For example if two obje...
Terminal Velocity For a body in free fall, the only force acting is its weight and its acceleration?g?is only due to gravity. The drag force increases as the body accelerates This increase in veloc...
Drag Forces Drag forces are forces acting the?opposite?direction to an object moving through a fluid (either gas or liquid) Examples of drag forces are?friction?and?air resistance A key component o...
前幾天，2022年夏季A-level大考成績開始放榜。 但在今日，英國《衛報》（the Guardian）爆料——在英國，約有2.8萬名A-level學生還沒有收到任何大學錄取通知書，面臨無大學可上的窘境。 約2.8萬英國學生目前沒有off...
