DPMT 2008
DPMT 2008
DPMT 2008
PHYSICS
1. A rod of length l and mass m is kept vertically on the ground. Its potential energy is
L L L
(1) mgL (2) mg (3) mg (4) mg
2 3 4
Sol: Ans [2]
L
u = Mg
2
L
is distance of e.m. from ground.
2
mgR 3
(1) mgR (2) (3) 2 mgR (4) mgR
2 2
GMm GMm
∆u = u f − u i = − −− .... (i)
2R R
mgR
∴ ∆u =
2
3. A body is projected at an angle 45º with horizontal. If escape velocity when projected vertically up
its escape velocity is 11.2 km/sec. What is new escape velocity ?
11.2
(1) km/sec (2) 11.2 2 km/sec (3) 11.2 km/sec (4) none of these
2
e
7. What is ratio of electron ?
m
(1) 2.76 × 1010 (2) 2.76 × 1010 (3) 1.76 × 1010 (4) 1.76 × 1011
charge
Charge = × total mass
mass
9. At what temperature iron becomes paramagnetic ?
(1) 200ºC (2) 400ºC (3) 600ºC (4) 800ºC
Factual
Factual
1
(3) ∝ (4) none of these
intensity
Pm = BkA and I ∝ A2
Factual
13. If charge and distance between them is reduced to half. Force between them
(1) remains same (2) increases four times (3) reduce four times (4) none of these
Use F = k .
q1q2
r2
14. A car of mass 400 kg is pulling a coach of mass 300 kg. If friction force is 1N/100 kg, what is
tension?
(1) 2100 N (2) 2126 N (3) 1926 N (4) 2750 N
4500 − 7
T = 300 × a = 300 × = 1926 N
400 + 300
m
15. Masses m and M on pulley move 0.6 m in 4 sec. What is ratio of ?
M
55 113 57 117
(1) (2) (3) (4)
57 117 55 113
Sol: Ans [No matching answer]
25 ( M − m) g
a= ⇒
t2 ( M + m)
16. Three rods of equal length of thermal conductivity k, 2k and 3k are symmetrically joined. If temperature
of ends are 0ºC, 50ºC and 100ºC respectively, what is temperature of function.
100 200
(1) 20ºC (2) ºC (3) ºC (4) none of these
3 3
Sol: Ans [3]
Factual
18. No. of beats between A and B is 5 Hz and between B and C are 3 Hz. Beat frequency between A
and C may be
(1) 1 (2) 2 (3) 8 (4) none of these
19. A gas at one atmosphere and having volume 100 ml is mixed with another gas of equal moles at 0.5
atm and having volume 50 ml in flask of one litre. What is their final pressure ?
(1) 0.5 atm (2) 1 atm (3) 0.75 atm (4) 0.125 atm
20. A body cools from 80ºC to 64ºC in 5 minutes nad same body cools from 80ºC to 52ºC in 10 minutes,
what is temperature of surrounding
(1) 24ºC (2) 28ºC (3) 22ºC (4) 25ºC
80 − 64 80 + 64
= k −T
5 2
80 − 52 80 + 52
= k −T
10 2
⇒ T = 24ºC
Factual
R = R0(A)1/3
At resonance φ = 0
2 2
1 1
z = R2 + = (100) +
2
−6
= 510 Ω
ωc 100 × 20 × 10
25. A body is moving forward and backward change in frequency observed of source is 2%. What is
velocity of the body (speed of sound is 300 m/sec)
(1) 6 m/sec (2) 2 m/sec (3) 2.5 m/sec (4) 3 m/sec
v −u
f1 = f
v
v+u
f= f
v
2u
f 2 − f1 = f .
v
∆f 2u
× 100 = × 100
f v
Solving u = 3 m/sec.
26. A body is projected horizontally with velocity 196 m/sec from height 400 m. What is time to reach
the ground.
(1) 5 (2) 10 (3) 15 (4) 20
Sol: Ans [2]
2h 2 × 400
t= = = 4 5 ; 10 sec.
g 10
27. Two spheres of unequal mass and unequal radius are released on inclined plane. They rolls down
with slipping. Which one will reach early.
(1) Lighter sphere will reach first (2) Heavier sphere will reach first
(3) Same time (4) none of these
Sol: Ans [3]
Body having larger acceleration will come down first.
g sin θ g sin θ
a= =
K2 1+
2
1+ 2
R 5
28. A cylinder is rolling down a inclined plane of inclination 60º. What is its acceleration
2g
(1) g/ 3 (2) g/ 3 (3) (4) none of these
3
∆L
× 100 = α × 10 × 100
L
∆V
× 100 = 3α × 10 × 100
V
Solving % change in volume = 3%
32. Water falls from height 100 m. Temperature of water
(1) increases (2) decreases (3) remains same (4) none of these
Sol: Ans [1]
Potential energy will convert into heat energy.
33. Two identical co-centric rings each of mass m and radius R are placed perpendicularly. What is the
moment of inertia about axis of one of the rings.
3 1
(1) MR 2 (2) 2MR2 (3) 3MR2 (4) MR 2
2 2
Sol: Ans [1]
MR 2 3MR 2
I = MR 2 + =
2 2
34. A motor of power 60 W draws current 5A from a source of 15 V. What is loss of power.
(1) 30 W (2) 25 W (3) 20 W (4) 15 W
Sol: Ans [4]
Loss = 15 × 5 – 60 = 15 W
35. An electron and proton are placed at distance 4.3 nm. What is dipole moment ? (C-M)
(1) 3.44 × 10–28 (2) 2 × 10–28 (3) 6.85 × 10–28 (4) none of these
Sol: Ans [3]
P = 1.6 × 10–19 × 4.3 × 10–9 = 6.85 × 10–28.
1
W = ∆K = × 10(10) 2 − 0 = 500 J
2
39. A stone is whirled in path of radius 1 m and its speed decreases from 4 m/sec. to 2 m/sec. in 2 sec.
What is angular acceleration ?
(1) 1 rad/sec2 (2) 2 rad/sec2 (3) 4 rad/sec2 (4) none of these
Sol: Ans [1]
Using v = u + at
a = –1 m/sec2
a
α= = 1 rad/sec2
R
40. What is nature of light and sound waves ?
(1) Light is transverse and sound is longitudinal
(2) Light is longitudinal and sound is transverse
(3) Both transverse
(4) Both longitudinal
Sol: Ans [1]
Factual
41. If the colour code of carbon resistor is as follows, then give the value of its resistance in KΩ.
Colour of I strip – yellow
Colour of II strip – blue
Colour of III strip – orange
Colour of IV strip – gold
(1) (46 ± 5%) (2) 0.46 ± 5% (3) 46 ± 10% (4) 0.46 ± 10%
Sol: Ans [1]
Using the sequence
B B R O Y G B V G W
0 1 2 3 4 5 6 7 8 9
For yellow strip use 4
For blue strip use 6
For orange strip use 103
For gold strip use 5%
Answer is (46 × 103 ± 5%) Ω or (46 ± 5%) kΩ
42. Self inductance of solenoid is proportional to
NA NA2 A N2A
(1) (2) (3) (4)
l l L l
Sol: Ans [4]
µ0 N 2 A
L=
l
bacd