Projectile Motion And Forces Pressure, Density Flashcards

1
Q

Projectile motion is:

A

Refers to an object that is in flight after bring thrown or projected.

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2
Q

Acceleration in projectile motion :

A

Acting in vertical direction which is acceleration due to gravity
No acceleration in horizontal direction hence constant speed.

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3
Q

To find vertical and horizontal components :

A

Use equations of motion separately applied in x and y axes to get unknown parameters

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4
Q

Vertical component of velocity _ going up the parabola, at _ point of path becomes _

A

Decreases
Highest
0

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5
Q

Angle between velocity (horizontal) and acceleration (due to gravity) at highest point is

A

90°

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6
Q

Gravitational field:

A

Provides force of attraction between masses

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7
Q

Uniform gravitational field :

A

Field lines parallel, same distance apart

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8
Q

Force depends on _ and _ which vary with planet

A

Mass and strength of gravitational field

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9
Q

Electric field:

A

Provides force of attraction/repulsion between charges

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10
Q

Fields equations :

A

F=mg, g is gravitational field strength

F=Eq, E is electric field strength as

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11
Q

Force depends on _ and _ (electric)

A

Size of charge and strength of E

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12
Q

Similarities between G and E fields

A
  • point charges and masses follow inverse square law
  • non contact forces ie exert force from distance
  • field strength defined in terms of force per unit N/kg or C
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13
Q

Differences between G and E fields

A
  • G can only be attractive while E be both attractive and repulsive
  • objects can be shielded from E but not G
  • E only act upon charted masses, G on all masses
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14
Q

What is upthrust

A

Force which pushes upwards on a object submerged in fluid ie liquid or gas

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15
Q

Upthrust is due to

A

Difference in hydrostatic pressure at top and bottom of immersed object

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16
Q

Upthrust/buoyancy is _ in liquid that gases, because _

A

Larger

Liquids are more dense

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17
Q

Upthrust/buoyancy is _ in liquid that gases, because _

A

Larger

Liquids are more dense

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18
Q

Hydrostatic pressure depends on _ that an object is submerged in from _. This means

A

Height/depth
P=pgh
Water pressure at bottom is greater than at top

19
Q

Explain what happens for upthrust

A

Upthrust is directly proportional to pressure. Force at bottom will be greater than at top. Resultant pressure causes resultant upward force on object called upthrust

20
Q

Object rises in fluid when _. Objects float when _

A

Upthrust is greater than weight

Objects density less than that of fluid

21
Q

Upthrust is influenced by _ not _

A

Pressure

Not density

22
Q

Drag force is

A

Force acting the opposite direction to an object moving through fluid

23
Q

Key component of drag :

A

Increase with speed

24
Q

Centre of gravity

A

Point at which weight of object may be considered to act (seems)

25
For symmetrical objects with uniform density where is centre of gravity located
Point of symmetry
26
2 factors affecting stability
-objects more stable when centre of gravity lies above base -wider the base lower centre of gravity hence more stable (centre of mass should be over base when crossed will topple)
27
What does and does bot depends on gravitational field
Centre of gravity does - W=mg where g is acceleration due to gravity Of mass doesn't
28
Centre of gravity of an object in space will be :
More towards object with larger gravitational field
29
Centre of gravity is a _ and changes with _
Hypothetical point | Shape of body
30
Moment is
Turning effect of a force. It is force multiplied by perpendicular disgrace from pivot
31
Moments occur when
Force causes object to rotate about pivot
32
SI unit for moment
Nm
33
Greater the - largee the moment with less - being applied
Distance | Force
34
What is a couple?
Pair of forces acts to produce rotation only.
35
Moment of a couple :
Doesn't depends on pivot, rather the perpendicular distance between the 2 forces
36
Couple has pair of forces that are:
- equal in magnitude - opposite in direction/parallel - perpendicular distance between them
37
Condition of couple
- produce resultant force 0, so F=ma and no acceleration | - lines of actions of forces don't meet
38
Turning effect or moment of couple called
Torque
39
Turning effect or moment of couple called
Torque
40
When line of action goes through pivot...
Perpendicular distance becomes 0 No moment Not a couple
41
Torque =
One of the forces × perpendicular distance between forces
42
Principle or moments:
For a system to be balanced or in equilibrium, sum of clockwise moments about a point must be equal to sum on anticlockwise moments about the same point
43
When a system is in equilibrium :
-no resultant force -no resultant torque Remains at rest or at constant velocity. No rotation
44
In equilibrium, coplanar forces are representated using
Closed Vector triangles. Form closed path where they follow each other