S1 Physics Definitions Flashcards
What is the definition for a vector quantity?
Vector quantities need 3 things to be fully defined, a magnitude, unit and a direction.
What is the definition for a scalar quantity?
Scalar quantities need 2 things to be fully defined, a magnitude and a unit.
What is Newton’s 1st law and what are it’s states of motion?
The forces on a system are balanced and so FR= 0, the object will not accelerate. The object has 2 possible states of motion;
- Stationary
- Moving at a constant velocity
What is Newton’s 2nd law
FR= m a, and so FR/ m = a; The acceleration, a of a body is directly proportional to the resultant force, FR, and inversely proportional to the mass, m.
What is the definition of mass?
Is a measure of the amount of matter of an object.
What is the definition of weight?
Is the size of the gravitational force acting on an object
What is the definition of Density?
Is the measure of the amount of matter of an object.
What is the definition of Hooke’s law?
The extension of a spring is directly proportional to the applied force up to the limit of proportionality.
What is the definition of pressure?
The force per unit area.
What is the definition of moments? (Calculation)
The product of Force (F) x perpendicular distance (d)
What is the definition of Principle of moments?
For a system in rotational equilibrium the sum of the clockwise moments= sum of the anti-clockwise moments about any point.
What is the definition of centre of mass?
The point through which the entire mass of the object appears to be concentrated.
What is the definition of centre of gravity?
The point through which the entire weight of an object appears to act.
What is the definition of atomic mass number?
17 - Atomic mass number – the number of protons and neutrons in an atom.
What is the definition of the atomic number?
18 - Atomic number – the number of protons in an atom.
What is the definition of ionisation?
19 - Ionisation – the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions.
What is the definition of an isotope?
20 - Isotope – variants of the same element with the same number of protons but varying number of neutrons.
What is the definition of half-life?
21 - Half-life – the average time taken for the number of radioactive nuclei to reach half its initial value, or the average time taken for the activity of a radioactive source to reach half its initial value.
What is the definition of activity?
22 - Activity – the number of disintegrations per second of a source.
What is the definition of background radiation?
23 - Background radiation – radiation that takes place naturally and is caused by radioactive material in rocks, the air and our bodies and partly by cosmic rays from outer space.
