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Flashcards in Physics 5 Deck (62)
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1

What force us created when a object is pulled along the ground?

Friction

2

How can friction be reduced

-Using rollers or wheels
- Having a smooth surface

3

What are the types of forces

-friction
-weight (gravity)
-upthrust
-magnetic
-electrostatic
-nuclear
-thrust

4

In what unit are forces measured

N -> newtons

5

Air resistance and water resistance are forms of....

Drag

6

When does the drag force increase?

When speed increases

7

Top speed

The maximum speed a object can go

8

Energy stores

-kinetic
-chemical
-thermal
-gravitational potential
-elastic potential
-sound

9

Law of conservation of energy

Energy is never created or destroyed only transferred or stored

10

Equation of speed

Speed= distance
—————–
time

11

Mean (average) speed

total distance
———————
total time taken

12

steep line on distance-time graphs

Means you are travelling quickly

13

Horizontal line on distance-time graph

Not moving at all

14

Relative speed

Add= if you are on a train and the train is moving at 50km/h and you move the same direction at 3km/h your relative speed is 53km/h
Subtract= if you are on a train which is moving at 50km/h and you move in the opposite direction at 3km/h your relative speed is 47km/h
Multiply=if two trains are traveling at 50km/h towards each other the are moving at a relative speed of 100km/h

15

Moment equation

Moment of the force = force x perpendicular distance from pivot
(N m) (N) (m)

16

Lever

A lever is a long bar that turns around the pivot

17

Pivot

The point where the object turns

18

Synonym for pivot

Fulcrum

19

Rule to move load

The longer the lever the easier it is to move the load

20

What does the lever do

Acts like a force multiplier if the effort distance is larger than the load distance

21

In equilibrium

When the forces are balanced

22

What are most machines used for

Use smaller force to move a object

23

Name 3 simple machines

-lever
-ramp
-pulley

24

Why are Ramos efficient

It needs less force to push a object up a ramp than it does to lift it directly

25

When is Less force needed in a ramp

The shallower the slope the less force needed, but more distance to reach its height.

26

Pulley rule

If the force is halved the distance the rope is has to be double

27

What does work mean

The amount of energy transferred when a force moves something

28

Formula to calculate work

Work done = force x distance moved
(J) (N) (m)

29

What is a force field

A force field is a space where a non-contact force has a effect

30

What are magnetic fields

The space around a magnet where it can attract magnetic materials

31

How can you find the shape of a magnetic fiel

Using iron fillings

32

Which objects have a gravitational field

All objects with a mass have a gravitational field

33

What happens when objects are in each other's gravitational field.

They attract each other

34

What is the earths gravity

~ 10N/kg

35

Equation for weight

Weight (N) = mass (kg) x g (N/kg)

36

What kind of forces are there

-magnetic fields
-gravitational fields

37

When can static electricity build up?

When two different materials rub together

38

What do atoms consist of

-a central nucleus with small particles called electrons moving around it.
-the nucleus has a positive charge and each electron has a negative charge.
-this way they are balanced
-the total positive and negative charges are usually the same.

39

What happens when you rub two insulating materials together

Some electrons may be transferred from one object to the other

40

Can the positive charges be tranfered

Because they are fixed to the nuclei of the atom

41

What happens to the object that ends up with more electrons

It has a overall positive charge

42

What happens when you rub a acetate rod with a piece of cloth

The acetate ends up with less negative electrons and has a overall positive charge, and the cloth has a overall negative charge.

43

What happens when you rub a polythene rod with a piece of cloth

The negative electrons from the cloth move to the rod making the rod negative and the cloth positive.

44

What can attract uncharged objects

Something with a charge of static electricity, it's very small normally just notice it with small things (e.g hair)

45

What is the electric field

The space around a charged object.

46

When is the field stronger

When it's closer to the object

47

What is a electric current

The flow of electrons, which are negatively charged particles

48

Series circuit: does the current vary?

No

49

Series circuit: do all the bulbs go off when a switch is opened

Yes

50

Series circuit: If you add more bulb to the circuit what will happen

The current is reduced and the bulbs get dimmer

51

Parallel circuit: is the current always the same

The current separates throughout the circuit because of junctions

52

Parallel circuit: how are the bulbs controlled

Each bulb is controlled individually (depending where the switch is placed)

53

Parallel circuit: what happens if you add more bulbs

The bulbs all stay at their original brightness, the current trough each bulb stays the same.

54

How do we measure current

With a ammeter (amps)

55

How do we measure the voltage

Using a voltmeter (volts)

56

What is resistance

A way of saying how easy or difficult it is for the current to flow through it.

57

Factors that affect resistance

-the longer the wire the higher the resistance
-the thicker the wire the higher the resistance
-insulators have a very high resistance

58

What are the units for for resistance

ohms

59

How do you calculate voltage

Voltage (V)= current (A) x resistance (ohms)

60

What is a electromagnet

A wire with a electric current flowing that has a magnetic field

61

How do you increase the strength of a electro magnet

-increasing the number of coils around the wire.
-increasing the current in the wire.
-using a magnetic material as a 'core' inside the coil of wire.

62

When does the direction of the magnetic change

When the current changes direction