2.2.3 Dynamics Flashcards
What is Newtons first law?
A body at rest remains at rest and a body in motion stays in motion until acted upon.
What is newtons second law?
F=MxA i.e the acceleration of an object is directly proportional to the force applied.
What is newtons third law?
Every action has an equal and opoosite reaction.
What is newtons third law sometimes referred too as?
Law of action and reaction.
What two forces does a body at rest experience on a horizontal surface?
Downward force due to gravity and the upward push of the surface.
What is mass?
The amount of matter in a body regardless of volume and position.
What is the formula for mass?
Weight (N) divided by gravity
What is the definition of weight?
The gravitational force of attraction between the mass of the earth and the mass of the object.
What is the formula for weight?
Mass x gravity
Does mass ever change compared to weight?
No, mass never changes, but weight changes depending on the gravity.
What is inertia?
The property that causes matter to resist change on its motion, the opposite to force.
What is work?
Force causing movement or displacement of an object.
In relation to work, what is said when the force is greater and the object moves further?
The greater the amount of work done.
What is the unit for work?
Joules
1 J = 1Nm
What is the formula for work?
Force (N) x distance (m)
What is power?
The measure of the rate at which work is done or at which energy is converted from one form to another.
What is the unit for power?
Watt
What is the formula for power?
Work divided by time.
What is energy?
The capacity to do work?
What is mechanical energy?
The energy held by a body after work is done.
What are the two types of mechanical energy?
Kinetic and Potential.
What is potential energy?
The energy a body has due to its position.
What is the formula for potential energy?
m x g x h
What is kinetic energy?
The energy a body has due to its motion.
What is the equation for kinetic energy?
Half MV squared.
What is total energy?
Total energy is the sum of all the different forms of energy in a system.
What is chemical energy?
Energy stored in the chemical bonds between atoms.
Is chemical energy a form of potential energy?
Yes
What is thermal energy also known as?
Internal energy.
What is the heat energy?
The heat that can flow from one body to another.
What is it important not too confuse heat energy with?
Temperature of a body.
What is efficency?
The proportion of energy added to a system that is transferred in useful ways.
What is the formula for efficency?
Energy out divided by energy in x 100,
What is momentum?
A vector quantity that describes mass in motion.
What happens to momentum if mass or velocity increase?
So does momentum.
What is the formula for momentum?
P= m x v =(kgm/s)
What happens in a closed system in relation to momentum?
The total momentum before an event = momentum after the event.
Is a closed system effected by external forces?
No
In a collision what happens to the kinetic energy and momentum?
Kinetic energy changes
Momentum is conserved
What are the two types of collision?
Elastic collisions
Inelastic collision
What happens to the kinetic energy in an elastic collision?
Kinetic energy is conserved.
What happens to the kinetic energy in an inelastic collision?
Kinetic energy is not conserved.
What is the equation for elastic collisions in terms of working out the recoil?
m1u1+m2u2=m1v1+m2v2
What two variables does an objects momentum depend on?
Its mass and its velocity.
What is the equation for impulse?
Force x time = impulse (Ns)
What is impulse?
The result of the force and time for which it acts on a body to change its momentum.
What is a gyroscope?
An instrument that contains a disc, called a rotor, rotating around an axis?
What two properties does the rotor in a gyro give?
Rigidity and Precession.
What is rigidity?
Newtons first law… the ability of the rotor to retain its axis unless acted upon.
What is rigidity caused by?
The inertia of the spinning mass, gyroscopic inertia.
What is the rigidity of the spinning rotor affected by?
Rotor mass
Effective radius
Speed
Bearing friction
What is precession?
If an external force is applied to change the direction of rotation, the gyro resists and moves the force at right angles.
What is the benefit of having a gyro with two gimbals?
It can rotate in any direction.
How can you get a vertical gyro to also show a digital pitch representation?
Add an electrical pick off.
When the body is on a horizontal surface what is the weight the same as in the friction formula?
Normal force, and therefore either can be swapped as long as its on a horizontal surface.
What is the formula for friction?
Friction= coefficent of friction x normal force
What is friction?
The force resisting relative motion of materials rubbing against each other.
What is starting friction?
When a body has been at rest just starts to move.
What is starting friction also referred too as?
Break away friction.
What is sliding friction?
The friction present as the body is sliding. It is always less than the starting friction.
What is rolling friction?
Present between a rolling body and the surface. It is greatly reduced when on wheels and is much smaller than sliding friction.
What does every pair of flat surfaces have? (friction)
Two different coefficents of friction.
What are the two types of coefficent of friction?
Start and slide.
