Section 4 - Mechanics and Materials: 4.1 - Mechanics Flashcards
(36 cards)
What is meant by a scalar quantity?
A quantity that has only magnitude.
What is a vector quantity?
A quantity that has magnitude as well as
direction.
Is acceleration a vector or scalar quantity?
Vector.
Is mass a scalar or vector quantity?
Scalar.
What is the difference between mass and weight?
Mass is scalar and is not dependent on the
gravity acting upon it. Weight is a vector and
depends on the gravitational field strength.
W = mg
If an object is in equilibrium the sum of the anti
clockwise moments would be …..
Equal to the sum of the clockwise
moments (principle of moments).
If an object is in equilibrium it means the object is …
Not accelerating, so is either:
● Stationary, or
● Moving at a constant velocity
How can the forces acting on a object be shown to be in equilibrium?
Adding the horizontal and vertical components of the forces acting on it, showing they equal zero.
Or if there are 3 forces acting on the object you can draw a scale diagram, if the scale diagram forms a closed triangle, then the object is is equilibrium.
What is a moment?
A turning force: force multiplied by the
perpendicular distance from the point to
the line of action of the force.
What is meant by a couple?
A pair of equal and opposite coplanar forces.
What is meant by the centre of mass?
The point through which all the mass of an object acts, for a uniform object the centre of mass is the centre of the object
If you have a uniform object, where
would its centre of mass be?
At the centre of the solid.
What can be described as ‘the change in
displacement per unit of time’?
Velocity, instantaneous velocity can be
found by measuring the gradient of a
tangent to a displacement-time graph
What is the area under a velocity-time and
acceleration-time graph?
The displacement travelled and the
velocity respectively.
As speed increases, so air resistance ….
Increases (proportional to the square of
the speed).
A ball if projected off a castle at 6m/s,
how does its horizontal velocity change
from its launch until it hits the ground?
The horizontal velocity remains the same
as there is no acceleration in that
direction.
How do the SUVAT equations reflect that all objects fall at the same rate?
Mass is not included in the SUVAT
equations, showing that the mass of an
object does not affect its speed or
acceleration.
In projectile motion, what is the vertical acceleration?
The vertical acceleration is equal to
gravitational field strength (g).
What is meant by terminal velocity?
When the forces acting on the falling
object become balanced, the
acceleration becomes zero and the
object is moving at maximum velocity.
What is meant by friction?
A resistance to motion between an object
and a surface or an object moving
through a fluid. Friction is a force that
acts in the opposite direction to the
movement.
Which of Newton’s Laws state ‘every action force
has an equal and opposite reaction force’?
Newton’s third law?
What is Newton’s second law?
Where mass (m) is constant, F is the
force applied and a is the acceleration.
What is Newton’s first law?
An object stays moving at a constant
velocity until a force acts upon it.
What is the difference between elastic
and inelastic collisions?
In an elastic collision the kinetic energy before is
equal to the kinetic energy afterwards.
In an inelastic collision the kinetic energy at the
end is not equal to the kinetic energy at the start.
