3.2 Forces In Action Flashcards
Describe what happens when a resultant force acts on a body with mass m
The body will accelerate in the direction of the resultant force. The resultant force is related to mass and accelerate by formula F=ma
Give 3 examples of common forces and explain briefly what they do
Weight-gravitational force acting on an object through its centre of mass
Friction- the force that arises when two surfaces rub against each other
Drag-the resistive force in an object travelling through a fluid
Tension-the force within a stretched cable or rope
Upthrust- the upward buoyancy force acting on an object rests against another object. Acts perpendicular to the plane of contact
What is meant by drag?
An object moving through a fluid experiences a drag force acting on it. Drag is a frictional force that opposes Motion. In air this is air resistance
What is meant by terminal velocity?
When the forces acting on the falling object become balanced so the resultant force is 0. The acceleration becomes zero and the object is moving at maximum velocity
What is the principle of moments?
For an object in equilibrium, the sum of the clockwise moments is equal to the sum of the anti-clockwise moments
What is a moment?
A turning force: force x perpendicular distance from the point to the line of action of force
What is meant by a couple?
A pair of equal and opposite coplanar forces that have equal magnitude and opposite direction, applied to a body parallel to each other but not along the same line
If you have a uniform object, where would it’s centre of mass be?
At the geometric centre of the object
Describe what is meant by density
The mass per unit volume of substance
Unit kg/m^3
Describe what is meant by pressure
The pressure is the normal force exerted on a surface per unit area. Pascals 1Pa=1N/m^2
Describe what is meant by pressure
The pressure is the normal force exerted on a surface per unit area. It is measured in Pascals
What is the force that an object submerged in a fluid experiences?
It experiences an upwards force called upthrust. This is because the pressure at the bottom surface of the object is greater than at its top surface
State Archimedes’ principle
The upthrust exerted on a body immersed in fluid, whether partially or fully submerged, is equal the weight of the fluid that the body displaces. An object will sink if the upthrust is smaller than the weight. For a floating object, it’s weight is equal to upthrust
