Mechanics Flashcards
What is meant by a scalar quantity
A quantity that has no direction only a magnitude
What is a vector quantity
A quantity that has a magnitude aswell as direction
Are the following vector or scalars:
1) Acceelration
2) Mass
1) vector
2) scalar
What is the difference between weight and mass
Mass is scalar, and is not dependant on the gravity acting on it.
Weight is a vector and is dependant of the gravitational field strength
w=mg
Define the principle of moments
If an object is in equilibrium the sum of the clockwise movements are equal to the sum of the anticlockwise moments
If the object is in equilibrium it means that:
the object has no resultant force (accelerating)
What is a Moment
A Turning force:
Force multiplied by perpendicular distance from the pivot 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 weight of an object acts
What is Velocity
How do you find it on a displacement time graph
Change in displacement / Change in time
Gradient of the tangent to the line of time you require
What’s the area under a velocity time and accleration time
velocity time - displacement
accleration time - velocity
Describe the relationship between air resistance and speed
Air Resistance is proportional to the square of the speed
In projectile motion what is the vertical and horizontal accleleration equal to
Horizontal - 0 ms^-2
Vertical acceleration = -g accelerating upwards
What is meant by terminal velocity
When weight due to gravity and air resistance acting on a falling object become balanced.
The acceleration becomes zero and the object is moving at its maximum velocity
What is meant by friction
a resistance to motion between an object and the atoms it is in contact with
Force Always Acts in the opposite direction to the motion
What is Newton’s third law
that every action force has an equal but opposite reaction force
What is Newton’s second law/
F= MA
Force applied is directly proportional to both the mass and the acceleration
What is newton’s first law
if the object is in equilibrium it will stay in motion or stationary until an external force acts upon it
What is the difference between elastic and in elastic collisions
Elastic collision —> KE before is equal to KE After
Inelastic collision —> KE before is not equal to KE after
Give an equation that can be used to calculate momentum
Mass*Velocity
What is always conserved in collisions?
Momentum
What is the rate of change of momentum
Force
What is an impulse
Change in momentum
Force*Time = Change in momentum
What does the area under a force time graph represent?
Change in momentum
What is power?
The rate of which work is done.
What is efficiency?
The useful power output / inputed power
Explain the principle of conservation of energy
Energy can opt be created or destroyed only transferred
Total energy within a system will always remain constant
It is given that before the collision the resultant momentum is acting to the right
For two cars of equal masses , traveling in opposite directions to each other
Describe the motion off the cars immediately after the collision if the collision is elastic.
Elastic Collisions conserve Total Kinetic energy
Any Collision conserves momentum
The trucks will not join and will be rebounded in opposite directions in order to conserve kinetic energy
Velocity of the car traveling originally to the left will have a higher velocity in order to conserve momentum
