Answer
of some questions of test conducted on 29.06.2015
Q. 1
Write C.G.S unit of force?
Dyne
Q. 2
State Newton’s first Law of motion.
It states that an object at rest will stay at rest and an object in motion will
stay in motion with the same speed and direction
unless acted upon by unbalanced force.
Q. 3
Why a cricket player moves his hand backward while
catching the ball?
By doing so the player increases
the time period in which the momentum of the ball is going to decrease. According to Newton's second law of
motion, the rate of change of momentum decreases. This results in lesser force
applied to hands of player i.e. magnitude of the force decreases
F = (mv-mu) / t.
Here force is indirectly proportional to the time. So lesser
impact on the hands of player.
If action is always equal to the reaction, explain how a horse can
pull a cart?
Q. 4
A stone of 1 kg is thrown with a velocity of 20 m/s across the frozen surface of a lake and comes
to rest after travelling a distance of
50 m. What is the force of friction between the stone and the ice?
Solution:
Given
Mass of stone, ms = 1 kg
Initial velocity,
u = 20m/s
Final velocity, v = 0 m/s
Distance
travelled, s = 50 m
We observe that
all values are in SI
To calculate:
Force, f = ma
We are to calculate
acceleration, a
Using 3rd law of
motion
v2 –u2 = 2as
(0)2 – (20)2 = 2 x a x 50
A = -4 m/s2
Now, F = ma
= 1 x – 4
= - 4 N…………………..Ans
Q. 5
If action is always equal to the reaction, explain how
a horse can pull a cart?
According to Newton's third law
of motion, action force is equal to reaction but acts on two different bodies
and in opposite directions. When The horse pushes the ground on backward direction
is the action whereas the ground pushes the horse in forward direction is the
reaction The force is able to overcome
friction force of the cart and it moves.
Q. 6
A boy of mass 40 kg jumps with a horizontal velocity 5m/s
onto a stationery cart with frictionless wheels. The mass of the cart is 3 kg.
What is his velocity as the cart starts moving? Assume that there is no
external unbalanced force working in horizontal direction
Solution:
Let v be the velocity
of the boy on the cart as the cart starts moving.
The total momenta
of the boy and cart before the interaction
40 × 5 + 3 × 0 = 200 kg m s–1.
Total momenta after the interaction
(40 + 3) × v = 43
v kg m s–1.
According
to the law of conservation of momentum, the total momentum is conserved during
the interaction. That is,
43
v = 200
⇒ v = 200/43 = +
4.65 m s–1.
Q. 7
A bullet of mass 4 g when fired with a velocity of 50
m/s, can enter a wall up to a depth of 10 cm. How much will be the average
resistances offered by the wall?
Solution :
(a)First of all write the given quantities
(b) Check if their units are in the same system, if not convert
the units.
Here
Mass of bullet, mb = 4 g (this
in in gram ; change it to SI system i.e. into kg.) =
4/1000 =.004 kg
Initial velocity of bullet, ub =
50 ms-1
Depth of penetration, s =
10 cm (this in in cm ; change
it to SI i.e. into meter.) =
10/100 = 0.1m
It is given that ball can enter the wall up to 10cm. Hence it
stops after penetrating into the wall after 10 cm.
So, final velocity of bullet, vb =
0
How much will be
the average resistances offered by the wall ?
This resistance the force.
We know that force, F =
ma
Here m
=0.004 kg, but a (acceleration is not known)
We should calculate the acc.(a) using 3rd law of motion
v2 –u2 = 2as ;
(0)2 – (50)2
= 2 x a x 0.1
a = -12500 m/s2
Now , F = ma
= 0.004 x – 12500
= - 50 N…………………..Ans
Q. 8
Deduce Newton’s 1st law mathematically by using
Newton’s 2nd law?
SECTION-II(BIOLOGY)
Q. 9
Name two different species of Indian cattle. What type
of food should be given to cattle? Explain
Species are
(a) Cow : Bos indicus
(b) Buffalo : Bos bubalis
Food Requirement: Cattle need
balanced diet containing all nutrients in proportionate amount. Food it fed for
following purposes.
For maintenance: This type of food
keep the animal healthy
For milching: Food required during
lactation for higher and good quality yield.
To fulfil above requirement
animals are given foods like:
(a) Roughage: It contains low nutrients
contents but is very source of fibres
and carbohydrate. It is dry, coarse and fibrous food. These are dried
straw of rice, wheat and leaves of cereal crops. Dry and green silage etc.
(b) Concentrates: It is rich nutrient
diet containing proteins, vitamins, fats and minerals like oilseeds and oil
cakes. Grains of gram, maize, bajra and jawar is also fed.
Apart from these, certain feed
additives containing micronutrients keeps the animal healthy and promote milk
output of dairy animals.
Q. 10 Name
Italian bee variety. Why it is considered ideal for honey production?
Apis mellifera
Apis mellifera is considered ideal for honey
production because:
(a) More honey collecting capacity
(b) Breeds well
(c)
Remains
in hives for a longer duration
(d) Can protect itself from other
(e) Gentle in nature
Q. 11 Why
are improved poultry breeds developed? Describe the desirable traits for which
new varieties are developed?
Solve yourself
Q. 12 Describe
composite fish culture system ? What is the major problem in fish
farming? How is it overcome?
In this usually a combination of 5
to 6 species of fish are selected for culturing in the same pond. These are selected
in in such a way that these have different food habits and prefer different
levels of water body to capture their food. Hence they don’t compete for food.
As a result food available in all parts of the pond is utilized. Different
combinations of fish are:
Indigenous: Catla, Rohu and Mrigal
Exotic: Silver carp, Grass
carp and Common carp
These are paired as
Catla and
Silver carp : being
surface feeder.
Rohus: Feed
in middle zone
Grass carps: feed
on weeds.
Mrigals and Common
carp: bottom feeders
Together these species can use all
the food in the pond without competing each other.
Major Problem:
Many of these fish breed only
during monsoon and their seed (egg) mixes. So there is lack of availability of
good quality seed.
How to overcome:
During breeding fish are kept in
separate pond and they are induced to breed using hormonal stimulation. It
ensures the availability of pure seed as there is no mixing now.
Q. 13 What
does the quality of honey depend upon?
Solve yourself
