Mechanics (AS) Flashcards
I am a quantity with size and direction. What am I?
Vector.
I am a quantity with size. What am I?
Scalar.
State Newton’s First Law.
The velocity of an object will not change unless a resultant force acts on it.
State Newton’s Second Law.
Acceleration is proportional to the force.
F = m x a
State Newton’s Third Law.
If an object A exterts a force on object B, then object B exerts an equal but opposite force on object A.
Galileo said: all objects fall at the _____ _____.
Galileo said: all objects fall at the (same rate).
A feather takes longer to fall than a brick due to air resistance. In a vaccum, they’d take the same time.
When does terminal speed occur?
You will reach a terminal speed when
the friction force = the driving force.
What is friction?
Friction is a force that opposes motion.
There are two types of friction:
‘dry friction’ between solid surfaces and
‘fluid friction’ (known as drag, fluid resistance or air resistance).
What do frictional forces convert kinetic energy into?
Heat and sound.
What is lift?
Lift is an upwards force on an object moving through a fluid.
When does lift occur?
Lift occurs when the shape of an object causes the fluid flowing over it to change direction.
In which direction does lift act?
The force acts perpendicular to the direction the fluid flows in.
What is momentum?
momentum = mass x velocity
p (kg/ms) = m (kg) x v (ms^-1)
What is a moment?
A moment is the turning effect of a force.
M = F x d
Where d is the perpendicular distance from the point to the line of action of the force (in m).
What is the principle of moments?
For a system to be in equilibrium,
sum of clockwise moments = sum of anticlockwise moments
What is a couple?
A couple is a pair of forces of equal size which act parallel to each other, but in opposite directions.
A couple is a ______ of forces of equal ______ which act ______ to each other, but in ______ ______.
A couple is a (pair) of forces of equal (size) which act (parallel) to each other, but in (opposite directions).
What is the centre of mass?
The centre of mass of an object is the single point that you can consider its whole weight to act through.
The centre of mass of an object is the ______ ______ that you can consider its whole ______ to act through.
The centre of mass of an object is the (single point) that you can consider its whole (weight) to act through.
How can you find the centre of mass of an irregular object?
- Hang the object freely from one point.
- Draw a vertical line downwards.
- Hang the object from another point.
- Draw another vertical line downwards.
The centre of mass should be where these lines cross.
