4.1 - Mechanics Flashcards
What is meant by a scalar quantity?
A quantity with only magnitude
What is a vector quantity?
A quantity that has magnitude and 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 a scalar and not dependent on the gravity acting upon it. Weight is a vector and depends on the gravitational field strength.
W =mg
If and object is in equilibrium the sum of the anticlockwise moments would be equal to what?
The sum of the clockwise moments
If an object is in equilibrium it mean the object is what?
Not accelerating so it is either stationary or at a constant velocity
How can forces acting on an object be shown to be in equilibrium?
1) Adding the horizontal and vertical components of force acting on it showing they equal 0
2) Or if 3 forces are acting on an object you can draw a force diagram and if it forms a closed circle the object is in 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 of the mass of an object acts, for a uniform object the centre of mass is in the centre of the object
What can be described as the change in displacement per unit time?
Velocity
What is the area under a velocity-time graph and an acceleration-time graph?
The displacement travelled and the velocity respectfully
As speed increases air-resistance does what?
Increases proportional to the square of the velocity
A ball projected from the top of a castle at a speed of 6m/s , how does its horizontal velocity change from then until it hits the ground
Horizontal velocity stays the same as there is no acceleration in that direction
How do the SUVAT equations reflect that all objects fall at the same rate?
There is no mass in the SUVAT equations , showing the mass of an object does not affect its velocity or acceleration
In projectile motion what is the vertical aceleration?
the vertical acceleration is equal to the gravitational field strength
What is meant by terminal velocity?
When the forces acting on a falling object become balanced, the acceleration becomes 0 and the object is moving at a maximum velocity
What is meant by friction?
The resistance to motion between an object and a surface or an object moving through a fluid. Friction is a force that acts the opposite direction to motion
Which of Newton’s laws state every action force has an equal and opposite reaction force?
3rd law
What is Newton’s second law?
F=ma or F= (mv-mu)/t
Rate of change of momentum
What is Newtons thirst law?
An object remains at a constant velocity if no external forces are acting on it
What is the difference between elastic and inelastic collisions?
Elastic conserves kinetic energy and momentum
Inelastic does not conserve kinetic energy but does conserve momentum
Give an equation that can be used to work out momentum
P = mxv Momentum = mass x velocity P= F x t Momentum = Force x time
True or False: linear momentum is only conserved in elastic collisions?
False , linear momentum is always conserved
What is Impulse ?
Change in momentum
Ft = mv
What does the area under a force time graph represent?
Impulse
Fscos(X) =?
work done/ energy transferred
What’s the rate of work done is equal to?
The power
What is efficiency ?
useful output power / input power
What is meant by the principle of conservation of energy?
Energy cannot be created or destroyed only transferred into other forms of energy
What is lift?
An upward force that acts on an object travelling in fluid , it is created by the object causing a change in the direction of fluid flow and acts perpendicular to the direction of fluid flow
