SPARKLING PHYSICS: 2012

Sunday, December 30, 2012

class test Time 45 min.

LEVEL 11
SUBJECT. PHYSICS
TOPIC.1ST AND 2ND LAW OF THERMODYNAMICS
Q1.Show that for an ideal gas Cp -Cv =R

_{where symbols have usual meanings.}

_{Q2.What is isothermal process. Derive an expression for isothermal work done.}

_{Q3.Explain the working of petrol engine with help of P-V diagram.}

_{Short answers questions}

_Q4_{(a) on what factors the efficiency of carnot engine depends ?}

_{(b) State 2nd law of thermodynamics.}

_{(c) write the limitations of 1st law of thermodynamics.}

_{(d) why Cp > Cv ?}

_{Best of luck .}

Wednesday, October 17, 2012

National Infotech College

1st terminal exam

subject:Physics class:11

group"C"

solution;

1Q: Given that
h=100m
u=10m/s
g=10m/s2
now ,h=1/2gt2, t=4.47s
s=ut ,s=44.7m
v=√u2+(gt)2
v=45.62m/s

2Q:Given that
frictional force(F)=200N
v=20m/s
now , power developed(p)=F.v
p=200×20=4000watt
p=4kw

3Q:Given that
s=200m
t=2s
using,s=ut+½at²
200=2u+2a………….(1)
now,s=420 and t=6s
420=6u+18a…………….(2)
from eqn.1 and 2,we get
a=-15m/s²and u=115m/s
final velocity(V)
at the end of 7th =u+at=10m/s

4Q:Given that
m1=7kg and m2=12kg
let T=tension and a=acceleration
for 12kg mass,T=mg-ma=m(g-a)
T=12(10-a)…………………(1)
and,for7kg mass,T=mg+ma=m(g+a)
T=7(10+a)…………………………(2)
from equation (1)and(2),we get
a=2.63m/s² and T=88.52N

5Q:Given that,20% of energy is retained by ice to melt it .
20%mgh=4.2(mx1000x80)
h=168000m=168km

6Q:Given that,
mass of ice=10gm at 0ºc
mass of water=15gm at20ºc
mass of vessel=100gm,and
sp.heat of vessel=0.09cal gm-1ºc-1
heat required to melt the ice(Q)=10x80
Q=800cal……………………(1)
heat lost by water and vessel to melt ice
Q’=(15x1+100x0.09)(20-0)
Q’=480cal…………………..(2)
clearly from eqn(1)and(2),the mass of ice melt
m=480/80=6gm
mass of ice remaining=4gm
result,total mass of water=21gm,ice=4gm,a toºc
alternative method
mass of ice remaining=
800-480/80=320/80=4gm

7Q:Given that,
vol.of copper vessel=1.80m³
initial temp=20°c
final temp=30°c
α for cu=16.7x10¯6/°c
γ=5.3x10ˉ4/°c
using ,vt=Vo(1+γt) for gly and for copper vessel
vol of gly spill out=vt(g)-Vt(cu)
V=1.80954-1.80090=0.00864m3

Saturday, August 18, 2012

class 11 questions

CLASS 11(PHYSICS)

SOME TYPICAL QUESTIONS

DIMENSIONS

1.Write the dimensional formula of G.

2. Write the dimension of

a.) R, In the following equation, PV=RT, where symbols have usual meaning.

b)The velocity v of a particle depends on time t according to relation
v =at+b/t+c ,what are the dimensions of a,b and c

3. Check the correctness of following equation,

a)s_nth=u+a/2(2n-1)

b) s=ut+1/2.at²
- EQUATION OF MOTION
4. A car is initially stationary. It has a constant acceleration of 2.0 ms^-2
                           a. Calculate the velocity of the car after 10s.
           b.Calculate the distance travelled by the car at the end of 10s.

     c.Calculate the time taken by the car to reach a velocity of 24ms^-2

^{5.A car is moving at 8m/s . The driver makes it at 1.0m/s for a distance of 18m. What is the final velocity of the car?}

^{6. A train travels at 50m/s when the driver applies the brake and gives the train a constant deceleration of magnitude 0.50m/s}²

^{for 100s. Describe what happens to the train. Calculate the distance travelled by the train in 1min. 40sec.}

^{7. A man walks for 1min. at a speed of 1m/s and then runs 1min. at 3m/s along a straight track. What is the average speed of the man ?}

^{8.The displacement of a particle moving in one dimension under the action of a constant force is related to time t by equation}

^t=√x+3

Where x is in meter and t is in second. Find the displacement of the particle when velocity is zero.

^{THE END}

Saturday, July 7, 2012

objective questions class12

Q;Cathode rays are stream of..................

Q:Cathode rays are produced when pressure in the discharge tube is of the order of......................

Q:The specific charge[e/m] of electron and proton are(1)................(2)............

Q;For determining(e/m) of electron by Thomson method , define the direction of electric and magnetic field to the motion of electron?

Q:If the speed of cathode rays is doubled for the value of electric field is needed so that the rays describe the same circular path is

QAn electron moving with velocity2X1O7m/s describe a circle in a mag.field0.02T,then the diameter of circle is.......

QAn electron at rest is accelerated through a pot.difference of 200volt.if the velocity of electron8.4X106m/s,the value of e/m of electron is.............

Q.If electrons enter normally in mag.field0.03Tdescribe circularpath of radius1.5cm,then the speed of electron is.....................

Tuesday, May 15, 2012

Answer key of physics group c hseb 2069 new course

9 . a . 3.53 m/s

b . v1 = 3.2 m/s v2 = 0.2 m/s (in magnitude)

c . 45 m

d. 4.33 X 10 ^ 4

10. a . time lost = 3.88 s

b . ice remaining = 72.5 g and ice melts = 27.5 g

c . 15 %

11. f1 = 26.66 cm f2 = -80 cm

12. 100 µF

Thursday, April 26, 2012

VISCOSITY

The property of fluids by virtue of which a backward dragging force or a viscous drag acts tangentially on the layers of the fluids in motions and it tries to destroy the motion of liquid is known as viscosity .

      The viscosity of liquid decreases with increase in temperature and vice versa .
             FLOW LINE:The path of an individual particle in a moving fluid is called a flow line.
          STEADY FLOW:If the overall flow of pattern does not change with time,the flow of liquid is called steady flow.

STREAMLINE AND TURBULENT FLOW :

The flow of liquid is said to be a streamline flow if each particle of liquid follows exactly the same path and the same velocity as its predecessor . A streamline may be defined as a curve, the tangent to which at any point gives the direction of flow of the liquid at that point
This holds good,however,only so long as the velocity of the liquid does not exceed a particular limiting value,called its critical velocity,beyond which the flow of the liquid loses all its steadiness and becomes zigzag,acquiring what is called a turbulent motion .

http://www.astarmathsandphysics.com/a_level_physics_notes/fluid_mechanics/a_level_physics_notes_laminar_flow_and_turbulence_html_m50e823a0.gif

Saturday, April 21, 2012

What is physics?

Physics is the study of nature and its law.
To understand nature is physics , and mathematics is the deluxe coach to take us there comfortably.

SURFACE TENSION

The property of liquid by virtue of which it behaves like a stretched elastic membrane with natural tendency to contract ( occupy ) minimum surface area . Thus a liquid surface is always in a state of tension .
It is also defined as the force per unit length acting tangentially and right angle on either side of an imaginary line drawn at the liquid surface .
ST=F/L

UNIT N/m

example :

The shape of the liquid drop is determined by the potential energy due to surface tension . For any given volume of liquid , minimum area is occupied by the sphere . When the area of the surface is minimum the potential energy is minimum due to surface tension . Hence the liquid drop is spherical in shape.

example :

Hot water is a better cleaning agent because the lower surface tension makes it a better "wetting agent" to get into pores and fissures rather than bridging them with surface tension. Soaps and detergents further lower the surface tension.

EFFECT OF TEMPERATURE :

The surface tension of water is 72 dynes/cm at 25°C . It would take a force of 72 dynes to break a surface film of water 1 cm long. The surface tension of water decreases significantly with increase in temperature as shown in the graph.

Hot soup is more tasteful than cold one.

The surface tension of hot soup is less than that of cold one and therefore hot soup covers more area of the tongue.He nce hot soup is more tasty than the cold one