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Turning Effect of Forces Flashcards

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1
Q

what are parallel forces?

A

if the direction of forces are parallel to each other, even if they’re in opposite direction.

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2
Q

what are like parallel forces?

A
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3
Q

what are unlike parallel forces?

A

the forces that are parallel but have directions opposite to each other

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4
Q

what is a resolution of force?

A

a process of splitting a force into two mutually perpendicular components which ultimately creates the same effect on the body that the single force would have created.

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5
Q

how can force be represented in terms of its components?

A

F= √Fx2 + Fy2
derive it.

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6
Q

how can the components of force be represented in terms of force?

A

Fx= F Cos θ
Fy = F Sin θ
derive it

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7
Q

how can we find the value of θ?

A

θ= tan -1 fy/fx
derive it

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8
Q

tan θ= ?

A

Fy/Fx
P/B

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9
Q

the magnitude of vector can be determined if the __________________ are known.

A

magnitudes of components are known.

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10
Q

how can we know the direction of vector?

A

right angle triangle
θ= tan -1 fy/fx
derive it

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11
Q

How head to tail rule helps to find the resultant of forces ?

A

It is a graphical method used to find the resultant of two or more forces
The tail of 2nd vector coincide with the head of 1st vector and so on .
The resultant of all vectors is obtained by coinciding the tail of 1st vector with the head of last vector .

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12
Q

what is axis of rotation?

A

a line about which rotation takes place
this line remains fixed during rotational motion, while other points of the body move in circle about it.

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13
Q

unit for torque?

A

Newton–meter Nm
kgm²/s²
ma x m

T=F X L
T= ma x m
T= Kg x m/s2 x m

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14
Q

unit for newton?

A

kg x m/s2
m x a

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15
Q

define torque?

A

the turning effect produced in a body about a fixed point due to applied force.

aka moment of force

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16
Q

what is the line of action of force?

A

the line along which a force acts.

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17
Q

difference between length and moment arm?

A

length= distance b/w force & axis of rotation.
moment arm= perpendicular distance b/w line of action of force & axis of rotation.

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18
Q

moment arm is represented by which letter?
muzzle?
recoil?

A

L
OR
r
muzzle velocity: Vf of bullet
recoil velocity: Vf of gun

Vf= final velocity

remember that recoil is for gun as only a gun recoil.

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19
Q

what does torque depend on? How?

A

torque depends on force and moment arm.
Increasing either the force or the moment arm (or both) will increase the torque produced in a rotational system.

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20
Q

τ=?
is torque vector or scalar?

A

τ = F * L
vector

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21
Q

what if the moment arm isn’t ⊥
to the applied force?

A

extend the line of action of force & take L ⊥ from the axis of rotation to the line of action of force.

22
Q

what is clockwise torque?

A

force capable of rotating a body in clockwise direction.

23
Q

which torque is taken as negative & positive?

A

clockwise = -ve
anticlockwise = +ve

24
Q

to tighten a nut, what direction force we need?
why is there a need for 2nd condition of equilbrium?

A

clockwise direction(cap)
The first condition (net force equals zero) ensures that the object does not experience translational acceleration.

The second condition (net torque equals zero) ensures that the object does not experience rotational acceleration.

Even if the net force is zero, an object could still rotate if there is an imbalance of torques.

25
Q

to loosen a nut, what direction force we need?

A

anti-clockwise direction

think about opening the cap of a bottle

26
Q

what is anti-clockwise moment?

A

the torque or moment of the force produced in anti-clockwise direction.

27
Q

state the principle of moment?

A

when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point.

28
Q

centre of mass?

A

The center of mass is the location in the body where all of the mass is concentrated. It is a point where an applied force causes the system to move without rotation.

29
Q

what is centre of gravity?

A

a point where the whole weight of the body appears to act vertically downward.

30
Q

what is centre of gravity of
1.square
2.circular disc
3.solid sphere
4. hollow cylinder
5. rectangle
6. triangle
7. circular ring
8. hollow sphere

A

page 95
1. point of intersection of its diagonals.
2. geometric centre
3. centre
4 mid point on its axis of
symmetry (same for cone)
5. point of intersection of its diagonals.
6. point of intersection of its medians
7. centre of ring
8. geometric centre

31
Q

how to find the centre of gravity of an irregular object?

A
  1. hang it randomly from three different points.
  2. connect/mark vertical lines drawn with the help of plumb line.
  3. these will meet at a common point which will be the CG.

plumbline: consists of small metal bob supported by a string. When suspended freely by the string, it rests along vertical direction due to its weight. CG of bob is exactly below its point of suspension.

32
Q

a force applied to centre of mass produces ___________.

A

translatory motion

33
Q

acceleration due to gravity __________ with altitude.
why is the base of a vehicle kept wide?

A

decreases
difference between centre of mass and CG.
because the vertical line passing through its CG should not get out of its base during a turn.

34
Q

Length = ?
to find a scale?

A

Length = Force / Spring constant
Length = 45N / 10N/cm = 4.5cm

35
Q

couple produces only ____________.
give one example in which an object satisfies first condition of equilibrium but is not in equilibrium?

A

rotation

36
Q

when is there a couple?

A

when two forces are:
parallel
opposite in direction
equal in magnitude
NOT along the same line of action.
and displaced by perpendicular distance or moment.

37
Q

what is a couple?

A

a couple is formed when a pair of equal and unlike parallel forces not along the same line of action of force act on an object.

38
Q

state an example of couple?

A

page 96

39
Q

what is the SI unit of couple?

A

Nm
Newton x meter

40
Q

what is couple arm?

A

the perpendicular distance between the lines of action of two forces or couple.

41
Q

what is the formula of couple?

A

τ = F * r

r=couple arm
F= any one force as both forces are equal in magnitude.

42
Q

what is equilibrium?
a body in equilibrium remains at ___________.

A

a body is said to be in equilibrium if it has no acceleration (linear or angular).
or no net forces acting on it.
rest or has uniform velocity.

43
Q

how many conditions are there for equilibrium. Name them.

A

2
ΣF=0
Στ=0

44
Q

what are the types of equilibrium? explain?

A

2
static
dynamic

45
Q

what is stability?

A

the ability of an object to return to its original position when the force that changed its position is removed.

46
Q

name the states of equilibrium?
if the line of action of force passes through the centre of mass of a body what would happen?

A

3
then the force cannot produce torque as the distance from the axis of rotation will become zero.
the body would move in the direction of the net force without rotation.

47
Q

why in stable equilibrium an object regains its position back?

or why it doesn’t fall over?

A

because its CG is at the lowest position meaning that by tilting the object’s CG will return back to previous position. cause CG doesn’t get out of base. When the object is tilted slightly, the force of gravity creates a torque (or moment of force) that acts to restore the object to its original position.

As long as the center of gravity stays within the base, the object will be stable

48
Q

why in neutral equilibrium an object’s CG does not rise or fall?

A

there is no moment to increase or decrease the displacement.

we just roll it not tilt it

49
Q

how can an object’s stability be improved?

A

lowering CM as possible by making it heavy at the bottom.
increasing area of support

50
Q

what is a point called where an applied force causes an object to move without rotation?

A

CM

physics (9 decks)

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