Projectile Motion And Forces Pressure, Density

Question 1

Projectile motion is:

Answer 1

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

Question 2

Acceleration in projectile motion :

Answer 2

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

Question 3

To find vertical and horizontal components :

Answer 3

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

Question 4

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

Answer 4

Decreases
Highest
0

Question 5

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

Answer 5

90°

Question 6

Gravitational field:

Answer 6

Provides force of attraction between masses

Question 7

Uniform gravitational field :

Answer 7

Field lines parallel, same distance apart

Question 8

Force depends on _ and _ which vary with planet

Answer 8

Mass and strength of gravitational field

Question 9

Electric field:

Answer 9

Provides force of attraction/repulsion between charges

Question 10

Fields equations :

Answer 10

F=mg, g is gravitational field strength

F=Eq, E is electric field strength as

Question 11

Force depends on _ and _ (electric)

Answer 11

Size of charge and strength of E

Question 12

Similarities between G and E fields

Answer 12

• 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

Question 13

Differences between G and E fields

Answer 13

• 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

Question 14

What is upthrust

Answer 14

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

Question 15

Upthrust is due to

Answer 15

Difference in hydrostatic pressure at top and bottom of immersed object

Question 16

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

Answer 16

Larger

Liquids are more dense

Question 17

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

Answer 17

Larger

Liquids are more dense

Question 18

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

Answer 18

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

Question 19

Explain what happens for upthrust

Answer 19

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

Question 20

Object rises in fluid when _. Objects float when _

Answer 20

Upthrust is greater than weight

Objects density less than that of fluid

Question 21

Upthrust is influenced by _ not _

Answer 21

Pressure

Not density

Question 22

Drag force is

Answer 22

Force acting the opposite direction to an object moving through fluid

Question 23

Key component of drag :

Answer 23

Increase with speed

Question 24

Centre of gravity

Answer 24

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

Question 25

For symmetrical objects with uniform density where is centre of gravity located

Answer 25

Point of symmetry

Question 26

2 factors affecting stability

Answer 26

-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)

Question 27

What does and does bot depends on gravitational field

Answer 27

Centre of gravity does - W=mg where g is acceleration due to gravity
Of mass doesn’t

Question 28

Centre of gravity of an object in space will be :

Answer 28

More towards object with larger gravitational field

Question 29

Centre of gravity is a _ and changes with _

Answer 29

Hypothetical point

Shape of body

Question 30

Moment is

Answer 30

Turning effect of a force. It is force multiplied by perpendicular disgrace from pivot

Question 31

Moments occur when

Answer 31

Force causes object to rotate about pivot

Question 32

SI unit for moment

Answer 32

Nm

Question 33

Greater the - largee the moment with less - being applied

Answer 33

Distance

Force

Question 34

What is a couple?

Answer 34

Pair of forces acts to produce rotation only.

Question 35

Moment of a couple :

Answer 35

Doesn’t depends on pivot, rather the perpendicular distance between the 2 forces

Question 36

Couple has pair of forces that are:

Answer 36

• equal in magnitude
• opposite in direction/parallel
• perpendicular distance between them

Question 37

Condition of couple

Answer 37

• produce resultant force 0, so F=ma and no acceleration

- lines of actions of forces don’t meet

Question 38

Turning effect or moment of couple called

Answer 38

Torque

Question 39

Turning effect or moment of couple called

Answer 39

Torque

Question 40

When line of action goes through pivot…

Answer 40

Perpendicular distance becomes 0
No moment
Not a couple

Question 41

Torque =

Answer 41

One of the forces × perpendicular distance between forces

Question 42

Principle or moments:

Answer 42

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

Question 43

When a system is in equilibrium :

Answer 43

-no resultant force
-no resultant torque
Remains at rest or at constant velocity. No rotation

Question 44

In equilibrium, coplanar forces are representated using

Answer 44

Closed Vector triangles. Form closed path where they follow each other