answer sheet

   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