AQA AS Physics - Mechanics and Materials
Exam Questions and Answers 100% Pass
Scalar
A unit with magnitude but no direction.
Vector
A unit with magnitude and direction.
What are the two methods for adding vectors?
Scale drawings and trigonometry.
Free-body force diagrams
Show all the forces acting on a body, each arrow shows the size and the direction of the force.
Equilibrium
The forces acting on a body are balances and it is not accelerating (it may be at rest or at a constant
velocity).
Moment
The turning effect of a force.
Moment equation
Force x perpendicular distance from the pivot.
Moment unit
Nm
If the moments on an object are not balanced,
it will turn.
Principle of Moments
For a body to be in equilibrium, the sum of the clockwise moments about a point must be equal to the
sum of the anticlockwise moments about the same point.
Levers
In a lever an effort force acts against the load force about a rigid object (the lever) attached to a pivot.
Couple
A pair of equal and opposite coplanar forces (they act parallel to each other).
What does a couple cause?
No resultant linear force, but a turning effect (a moment).
, The moment created by a couple
The size of the moment depends on the size of the forces and the distance between them.
Couple equation
Moment of a couple = size of one force x perpendicular distance between the forces.
Centre of mass
The point at which the mass of the object acts.
Where is the centre of mass of a uniform, regular solid?
At its centre.
The centre of mass can be found through...
Symmetry and experiment (hanging it and drawing a vertical line down, repeating this - where the
lines cross is where the centre of mass is).
How can centre of mass be used to stabilise objects?
If the line drawn downwards from the centre of mass passes within the base area, then the object will
be stable.
Free fall
The motion of an object undergoing acceleration due to gravity.
The only force acting on an object in free fall
Weight
Objects in free fall...
accelerate at the same rate.
Newton's first law
An object will remain at rest or at a constant velocity as long as there is no resultant force.
If the forces on an object aren't balanced, it will...
accelerate
Newton's second law
The resultant force is proportional to the acceleration of the object (F = ma)
Newton's third law
Each force has an equal and opposite reaction force.
Friction
A force that opposes motion.
Exam Questions and Answers 100% Pass
Scalar
A unit with magnitude but no direction.
Vector
A unit with magnitude and direction.
What are the two methods for adding vectors?
Scale drawings and trigonometry.
Free-body force diagrams
Show all the forces acting on a body, each arrow shows the size and the direction of the force.
Equilibrium
The forces acting on a body are balances and it is not accelerating (it may be at rest or at a constant
velocity).
Moment
The turning effect of a force.
Moment equation
Force x perpendicular distance from the pivot.
Moment unit
Nm
If the moments on an object are not balanced,
it will turn.
Principle of Moments
For a body to be in equilibrium, the sum of the clockwise moments about a point must be equal to the
sum of the anticlockwise moments about the same point.
Levers
In a lever an effort force acts against the load force about a rigid object (the lever) attached to a pivot.
Couple
A pair of equal and opposite coplanar forces (they act parallel to each other).
What does a couple cause?
No resultant linear force, but a turning effect (a moment).
, The moment created by a couple
The size of the moment depends on the size of the forces and the distance between them.
Couple equation
Moment of a couple = size of one force x perpendicular distance between the forces.
Centre of mass
The point at which the mass of the object acts.
Where is the centre of mass of a uniform, regular solid?
At its centre.
The centre of mass can be found through...
Symmetry and experiment (hanging it and drawing a vertical line down, repeating this - where the
lines cross is where the centre of mass is).
How can centre of mass be used to stabilise objects?
If the line drawn downwards from the centre of mass passes within the base area, then the object will
be stable.
Free fall
The motion of an object undergoing acceleration due to gravity.
The only force acting on an object in free fall
Weight
Objects in free fall...
accelerate at the same rate.
Newton's first law
An object will remain at rest or at a constant velocity as long as there is no resultant force.
If the forces on an object aren't balanced, it will...
accelerate
Newton's second law
The resultant force is proportional to the acceleration of the object (F = ma)
Newton's third law
Each force has an equal and opposite reaction force.
Friction
A force that opposes motion.
