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Grade 12 Physics > Force Fields > Flashcards

Force Fields Flashcards

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1
Q

What is a field

A

A space in which one object exerts a force on another object without touching it.

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2
Q

At what distance does the moon stay in an orbit around the earth and why ?

A

At around 400 000 km because of the earths gravitational pull.

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3
Q

What objects create a gravitational field around them

A

All masses create a gravitational field around them

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4
Q

How would you represent the earths gravitational field by drawing

A
  • earth in the centre
  • straight lines drawn around earth (not touching)
  • arrows on lines pointing towards earth to show direction
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5
Q

What do the arrows on a diagram of the earths gravitational field represent

A

The direction of the gravitational force on the objects placed in the field

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6
Q

What does the spacing of the lines in a diagram of the earths gravitational field represent

A

The strength of the gravitational field

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7
Q

What happens to gravitational force as we move away from the earth

A

It gets weaker

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8
Q

What happens to gravitational force as we love away from the earth

A

It gets weaker

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9
Q

What happens to gravitational force as we move away from the earth

A

It gets weaker

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10
Q

Why do we say the earths gravitational field is radial

A

the lines diverge racially from the centre of the Earth

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11
Q

What is Newton’s third law of motion

A

Two particles interact with each other and therefore exert equal forces on each other

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12
Q

What is Newtons law of universal gravitation

A

Every particle in the universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres

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13
Q

What is newtons law of gravitation in formula form

A

F = G (m1m2)/r^2
Nb! Everything is in SI units

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14
Q

What is G known as

A

The universal gravitational constant that sets the strength of the gravitational interaction in the sense that if it were doubled, so would all the gravitational forces be doubled. G=6,7 x 10^-11 Nm^2.kg^-2

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15
Q

What is the relationship between F and m1 in Newton’s Law of Universal Gravitation formula

A

F is directly proportional to m1

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16
Q

What is the relationship between F and m2 in Newton’s Law of Universal Gravitation formula

A

F is directly proportional to m2

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17
Q

What is the relationship between F and 1/r^2 in Newton’s Law of Universal Gravitation formula

A

F is directly proportional to 1/r^2

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18
Q

What is a gravitational field

A

The force acting per unit mass

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19
Q

What is weight (Fg)

A

the gravitational force the Earth exerts on any object on or near its surface

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20
Q

What is the weight of an object m by means of calculation

A

Fg=mg

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21
Q

What is the value of the gravitational field g near the earths surface

A

9,8m.s^-1

22
Q

What are the three formulas to find the gravitational force between the object of mass m and the Earth

A

F = GMem/r^2

mg = GMem/r

g = GMe/r^2

Where Me is the mass of the earth

23
Q

How do we calculate the acceleration due to gravity on any planet using the equation

A

g = G Mplanet / (Rplanet)^2

24
Q

What happens to field strength as distance increases

A

it decreases as the distance R increases

25
Q

What is an electric field

A

that region around a charged object in which another charged object will experience a
force

26
Q

What determines the direction of an electric field at a point

A

The direction of an electric field at a point is the direction in which a small positive charge would move
(under the influence of the field) if placed at that point.

27
Q

What are the two types of electric charge

A

Positive and negative

28
Q

What will happen if like charges are brought near each other

A

They will repel

29
Q

What will happen if unlike charges are brought near each other

A

They will attract

30
Q

What is charge measured in

A

Coloumb (C)

31
Q

What is coloumbs law

A

Two point charges in free space or air exert forces on each other. The force is directly proportional to the product of the charges and inversely proportional to the square of the distance between the charges

32
Q

What is a point charge

A

a charged particle with insignificant size and mass, which carries an electric charge.

33
Q

When will a point charge experience an electrostatic force

A

When it is brought near another point charge

34
Q

What is the relationship between the electrostatic force F and q1 and q2 in coloumbs law

A

F is directly proportional to q1 and q2

35
Q

What is the relationship between the electrostatic force F and r^2 in coloumbs law

A

F is inversely proportional to r^2

36
Q

What happens to the size of electrostatic force F when the magnitude of the charges increases

A

F increases

37
Q

What happens to electrostatic force F when the distance between the charges increases

A

F decreases

38
Q

Is electrostatic force a force of attraction or repulsion

A

It can be either, you need to look if the charges mentioned are like charges (repel) or opposite charges (attract)

39
Q

What is the formula to calculate electrostatic force

A

F = kq1q2/r^2

40
Q

What is k in the formula to calculate electrostatic force

A

where k is Coulomb’s constant = 9,0 x 10^9 N·m^2·C^-2

41
Q

What Is used to determine if there is an electric field in a certain region

A

A small charged particle is placed in the region.

◦ If the test charge experiences a force there is an electric field in the region.
◦ The direction of the electric field is always the direction in which a positive point test charge
moves.
◦ Field lines move from positive to negative.

42
Q

What is the magnitude of the electric field at a point

A

The force per unit charge

43
Q

What are other names for the magnitude of an electric field

A

It can also be called The electric field strength or the electric field intensity

44
Q

What type of quantity is Force

A

A vector quantity and thus it should always have magnitude and direction !!!

45
Q

What formula is used to calculate the magnitude of an electric field

A

E = F/q

Nb! q is charge experiencing electric field

46
Q

What is the direction of an electric field

A

The direction of force acting on a positive test charge is taken as the direction of the electric field intensity at any point in the field. The electric field radiates outwards from a positive point charge.

47
Q

What is another formula to calculate the magnitude of an electric field

A

E = kQ/ r^2

Nb! Q is charge responsible for electric field

48
Q

How do we calculate the resultant electric field for two charges

A

A vector sum of the two fields is calculated

49
Q

What are electric field lines

A

These are imaginary lines that will indicate direction and magnitude of the field

50
Q

What are the properties of electric field lines (6)

A

◦ They are imaginary
◦ They are solid lines
◦ The never cross each other
◦ always form a 90 degree angle with the object it originates from
◦ Will point away from a positive charge and towards a negative charge
◦ The density of the lines indicate the field strength

51
Q

What is electric field intensity measured in

A

N.C^-1

52
Q

What does a positive answer indicate for electric field intensity

A

A direction away from the charge

Grade 12 Physics (2 decks)

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