Easy way to learn science: 2012

Important Question from Simple Machine

1)Why are winding roads made on the hills?
Winding rads are made on the hills because winding roads are the form of inclined plane having longer
distance and makes our work easier my magnifying force.

2)Why is the efficiency of a simple machine is
always less than 100%?
When the output work is equal to the input work,but some part of the input work is lost in overcoming friction,the efficiency of a simple machine is always than 100%.

3)Why is it easier to apply force downward?
It is easier to apply force downwards because the force is applied influence the gravity.

4)Why is the blade of a metal cutter shorter than that of scissors used by tailors?
In metal cutter the effort distance is greater. Metals are very hard. In order to cut the metals we need more energy and effort.If the effort distance is greater than load distance there will be magnification of force and the metals would easily could cut.So  the blade of a metal cutter shorter than that of scissors used by tailors.

5)How does a wedge work?
When we apply effort the sharp end passes inside the material and cut the things.In this way wedge works.

6)How does wheel and axle work?
Wheel and axle is a co-axial two cylinder .the ropes
are wound around the wheel and the axle.The ropes are wound in opposite direction.The effort is applied in the big cylinder and load is lifted by a small cylinder. When the rope is wound around the wheel is pulled downward,the load wounded around the axle is raised upward.

7)Why is the mechanical advantage(MA) more in movable pulley?
The mechanical advantage is more in a movable pulley because it moves up and down changing its position. Due to which ED is greater than LD which helps in magnification of applied effort.

8)What is the method used to increase the mechanical advantage of a inclined plane?
There is only one method to increase the mechanical advantage of a inclined plane that is increasing the length of slope which increases of mechanical advantage of an inclined plane.

Inclined Plane

Inclined plane

Inclined Plane is a slope ramp which is used to lift the load a gradually by using less effort.It is a force multiplier.

The distance where the load should be taken is length of slope or distance travelled by effort. It is denoted by "l".

The length of height of slope is the distance travelled by load.

VR = length of slope
length of height of slope
= l
h

"OR"

VR = distance travelled by effort

distance travelled by load

= l

Wheel and axle

Wheel and axle
The type of simple machine which consist of two co-axial cylinders of different diameters which a mounted on the axle.

Diameter

A diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle.

Radius

Radius is a line segment from the center to the perimeter (surrounding area) of a circle. Half of a diameter is the length of radius.

In wheel and axle radius is the effort distance.
Radius of wheel is denoted by capital r "R" where as radius of axle is denoted by small r "r".

# Generally effort is applied in a big cylinder and load is applied on a small cylinder which means ED is greater than LD.

Mathematically,
VR = ED
LD
= Radius of wheel
Radius of axle
= R
r
Therefore VR of wheel and axle is = R

We know radius of wheel is greater than the radius of axle which makes the VR greater than 1 and more easy by magnification of force.

Types of Simple Machine

Types of Simple Machine
There are Six types of lever. They are:-
1) Lever 4) Inclined Plane
2) Pulley 5) Screw
3) Wheel and axle 6) Wedge

Lever
Lever is a rigid bar which is capable to rotate a fixed point called fulcrum.

Rembemer:- If the effort distance is greater than load distance magnification of force is there and the work can be done easily

Fulcrum is denoted as Δ , load as ¨ effort as $or# in the figure.
There are three types of lever. They are:-
1) First class lever
2) Second class lever
3) Third class lever

First class lever
The lever in which fulcrum is between load and effort is called first class lever.

In First class lever
Ld < Ed
Ld > Ed
Ld = Ed
Ld ≠ Ed

Second class lever
The type of lever in which load is in between fulcrum and effort.

In Second class lever Ed is always greater than load distance which magnification of force and make our work easier.

Third class lever
The type of lever in which effort is between fulcrum and load.

In Third class lever Ld is always greater than Ed in which there is no magnification of force and makes our work more difficult. MA of Third class lever is less than 1.

Ratio defination and formula

Mechanical Advantage (MA)
Mechanical Advantage of a machine is defined as a ratio of a load overcome by the machine to the effort applied in the machine.
Mathematically,
MA= load
effort
i.e MA= L

It has no unit as it is the ratio of two force.

What is meant by a simple machine having MA3?

It meant that we can overcome the load of 3 Newton (N) by applying the effort of 1N using simple machine.

Velocity Ratio (VR)
Velocity Ratio is defined as a ratio of effort distance to load distance.

Mathematically,

VR= effort distance

load distance

i.e VR= ED

Efficiency

It is the ratio of work output to work input per 100%.

Mathematically,

Efficiency= Work output

Work Input

= L Í LD

E Í ED

= L Í LD

E ED

= L ÷ ED

E LD

= MA ÷ VR
= MA
VR

i.e Efficiency= MA
VR

Important Question

Rest and Motion are relative terms . Why?
Rest and motion are relative terms because if we suppose a tree on the roadside.It is the state of rest as it is not changing its position with respect to a moving car but a car changes it position with respect to the tree. As,it is the state of motion, Therefore the treee is at rest but the running car is in motion relative to the tree. Hence rest and motion are relative terms.

Difference Between

Difference between scalar and vector quantity

_Scalar	_Vector
_{The quantities that have magnitude but no direction is called scalar quantity.}	_{The quantities that have both magnitude and direction is called scalar quantity.}
_{It is denoted by ‘A’}	_{It is represented by arrow head with}
_{It is measured by certain degebric matter.}	_{It is added by certain vactor rule.}
_{Sum of scalar quantity is always positive}	_{Sum of scalar quantity can be positive, negative or zero}

Relative motion

Relative motion
Motion of a body is described in the terms of motion of another body is called relative motion

Relative velocity
The relative velocity is defined as the velocity of the body with respect to another body
"OR"
It is also defined as a distance between of two bodies.

There are three cases of relative motion . They are:-

Case 1
When in opposite direction

V_AB = Relative velocity

timetaken

= 75 km + 90 km

1hr

= 165 km/hr

Conclusion

V_AB₌V_A+V_B

Case 2

When in same direction

V_AB₌100-80

= 20 km/hr

Conclusion

V_AB₌V_A-V_B

V_AB₌V_B-V_A

Case 3

If two bodies are moving uniformly i.e. they are moving in the same direction with same velocity then the relative velocity = 0

Acceleration

Acceleration

The rate of change per unit time is called acceleration.It is a vector quantity and it is denoted by "a".In SI System unit of a acceleration is m/s².

Initial Velocity= u
Final velocity = v
Time taken = t
Acceleration = Final velocity - initial velocity
Time taken
= v-u
t
Note*

# If a body starts from rest to motion u= 0

# If a body suddenly stops due to the application of external force, like- by applying brakes, v=0

# If a body is thrown vertically upward, at maximum height, v = 0

Motion

Motion
If a body changes its position with respect to its surrounding it is said to be in motion

Rest
If a body does not changes its position with respect to its surrounding it is said to be in rest .

Reference Point
The point about which we study the motion of an object is called reference point.

Uniform Motion
If a body travels equal distance in equal interval of time, the body is said to be in uniform motion

Non-Uniform Motion

If a doesnot body travels equal distance in equal interval of time, the body is said to be in non- uniform motion.

Speed
The rate of change of distance per unit time is called speed.
Speed=Distance travelled
Time taken
= m
s
= m/s
Therefore, SI Unit of speed is m/s

Velocity

The rate of change of displacement per unit time is called speed.

Velocity=Dislacement

Time taken

= m

= m/s

Therefore, SI Unit of velocity is m/s

Distance Travelled
The length of a path travelled by a moving body in any direction is said to be in distance travelled.Its is a scalar quantity and it has magnitude (having unit) but no direction.It is measured in meter(m) in SI Units.

Displacement
The shortest distance between two points is called displacement.It iis a vector quantity.In SI System Unit of displacement is meter(m).The shortest is always the straight line.

Difference between mass and weight

Difference between mass and weight

Mass	Weight
The amount of matter contained in a body is called mass.	The force of attraction exerted by Earth to pull an object towards its center is called weight.
It is constant.	It varies from place to place.
It is measured in beam balance.	It is measured in spring balance.

Important definination and notes

Time
It is defined as the interval between the two events.
The SI Unit of time is Second.

Mean Solar Day
The time taken by Earth to rotate around its axis is called 1 Mean Solar Day.
1 Mean Solar Day = 24 hr
= 24 x 3600 s
= 86400 s.

1 Second

It is defined as 1/86400 of a mean solar day.
1 minute =60 second (sec)

1 hour =3600 second (sec)

Length
The distance between two points (ends) is known as length. Its SI Unit Is Meter.

Volume
The space occupied by a body is called volume. Its SI Unit is Cubic Meter (m³).
Note *

Volume of a regular shape is calculated by using their respective formula i.e. V= LXBXH

Volume of a irregular body is measured by displacement method.

Area
The total space covered by a body is called area. Its SI Unit is square meter (m²).
Note *
Area of a regular body is found by using their respective formula i.e. A = LXB

Area of a irregular body is formed by plotting in a graph

Multiples and sub-multiples of

METER
mm cm deci m deca hm km

1 Meter = 10 decimeters (dm)
1 Meter = 100 centimeters (cm)
1 Meter = 1000 millimeters (mm)
10 Meter = 1 decameter (dm)
10 decameter = 1 hectometer (hm)
10 hectometer = 1 kilometer (km)

KILOGRAM

mg mm deci g deca hg kg

1 Tonne = 1000 kilograms (kg)

1 Quintal = 100 kilograms (kg)

1 kilogram = 1000 grams (g)

1 gram = 1000 milligram (mg)

System

SI SYSTEM

It is known as Standard International System of Units which is the improved and extended Version of MKS SYSTEM.

SYSTEM OF UNITS

CGS SYSTEM [FRENCH System of Measurement]
Length= Centimeter (cm)
Mass = Gram (g)
Time = Second (s)

FPS SYSTEM [BRITISH System of Measurement]

Length= Foot

Mass = Pound

Time = Second (s)

MKS SYSTEM [METRIC System]

Length= Meter (m)

Mass = Kilogram (kg)

Time = Second (s)

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