A force of 1N will give a 1kg mass an acceleration of 1ms−2 in the direction of the force
weight is a force based on the gravitational pull of the planet
mass the the amount of matter an object is made of
Weight (N) = mass(kg) x gravitational field strength (N/kg)
A newtonmeter shows the gravitational force acting on an object, in Newtons
Weight is the gravitational force acting on an object through its centre of mass
Friction is the force that arises when two surfaces rub against each other
Drag is a resistive force on an object travelling through a fluid
Tension is the force within a stretched cable or rope
Upthrust is the upward buoyancy of an object in a fluid
normal contact force is the force that arises when objects rest against each other
A fluid is a liquid or gas
magnitude of drag depends on speed, cross sectional area, texture, and density of the fluid
drag = speed2
Terminal velocity is reached when air resistance equals weight in the opposite direction
The centre of gravity is the point where the entire weight of an object appears to act
The centre of mass is the point at which any externally applied force produces a straight line motion but no rotation
experiment to find the centre of gravity : pins in an object and use a plumbline to draw lines - centre is the point of intersection
Conditions for equilibrium
resultant force of zero - horizontally and vertically
no rotation
When an object is in equilibrium, the forces acting on it form a closed triangle
The moment of a force is the turning effect of a force about some axis or point
The SI unit for a moment of a force is Nm
moment = force x perpendicular distance to the line of action of the force
The Principle of Moments
For a body in rotational equilibrium, the sum of the anti clockwise moments about any point its equal to the sum of the clockwise moments about that same points
Principle of Moments
ΣMclockwise=ΣManticlockwise
Applying a pair of equal but opposite forces parallel to each other along different lines causes a rotation without any translational motion
A couple is pair of equal but opposite forces parallel to each other that act along different lines
Torque of a couple = one of the forces x the perpendicular separation between the forces
Density = mass / volume
To find the volume of an irregular object, put the object in a container with a known volume of liquid and calculate the increase of volume
Pressure is the normal force exerted per unit of cross sectional area
Pressure
ρ=F/A
Gases and liquids exert pressure on surfaces as there is a constant movement of particles which collide with the surface
Pressure exerted by a vertical column of liquid = height of the column x density of the liquid x the value of acceleration under free fall
Pressure doesn't depend on the cross sectional area
density is directly proportional to height of a vertical column of liquid so pressure increases with depth
Denser liquids will exert greater pressure
Upthrust is the resultant force due to pressure of an object submerged in a fluid
Objects submerged in fluids exert pressure on the fluid which exerts pressure on the object which causes an upward force