WORKSHEET-39

PHYSICS Full Book

Worksheet-39
Topics:- Full Book
1. Two trains are each of length x meters moving parallel towards USE THIS SPACE FOR
each other at speeds 10 m/sec and 15 m/s respectively, what must SCRATCH WORK
be the value of x if they cross each other in 4 sec.
A.100 m B. 50 m
C. 200 m D. 25 m
2. Of the following transitions in a hydrogen atom, the one which
gives an absorption line of highest frequency is:
A. n = 2 → n = 3 B. n = 3 → n = 2
C. n = 3 → n = 8 D. n = 8 → n = 3
3. When the electron in a hydrogen atom jumps from the second orbit
to the first orbit, the wavelength of the radiation emitted is .
When the electron jumps from the third to the first orbit, the
wavelength of the radiation emitted is:
9 4
A.  B. 
4 9
27 32
C.  D. 
32 27
4. A particle is moving eastwards with a velocity of (5 sec) 5 m/sec. In
10 sec the velocity changes to 5 m/sec north wards. The average
acceleration in this time is:
A. Zero
B. 30 west of north
2
C. 1/ 2m / sec towards north west
D. 60 east of north
5. Work is always done on a body when:
A. A force act on it
B. It moves through a certain distance
C. It experiences an increase in energy through a mechanical influence
D. None of above
6. X-rays are produced during which of the following periods of time
of A.C voltage provided to accelerated electrons from cathode to
anode in a Coolidge tube?
A. 1st and 3rd quarter cycles only
B. 2nd & 4th quarter cycles only
C. Positive half cycle only
D. Negative half cycle only
7. An electron moves along + X-axis direction such that equation for
the voltage applied along axis is V=10-2(x). As the value of “x”
increase what will be the effect on it’s speed and it’s potential
energy respectively?
A. Increases, increases B. Decreases, decrease
C. Increases, decreases D. Decreases, increases
8. In S=at+bt+ct2, “S” is measured in meter and “t” in seconds. The
unit of “c” is:
A. m/s2 B. m/s
C. m D. None of these
9. A 20 g bullet moving with velocity 100 m/s strikes a block of mass
999 g at rest and gets embedded in it. The loss in K.E will be:
A. 100% B. 95%
C. 25% D. 50%

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10. Certain extremely dense neutron stars are believed to be rotating at

about 1 rev/sec. If such a star has a radius of 20 km, the acceleration
of an object in m/s2 on the equator of star will be:
A. 8105 B. 20103
6
C. 1210 D. 4108
11. When an ideal fluid passes through a constructed part of pipe it’s.
A. speed increases, pressure decreases
B. speed increases, pressure increases
C. speed decrease, pressure decreased
D. none of these
12. We have a liquid contained in a container of height H=20m in
H
which liquid height is . At what depth we must do the hole such
4
that stream of liquid hits the ground at a maximum horizontal
distance from base of the container?
H H
A. B.
2 4
H H
C. D.
6 8
13. Which of the following statements is false?
A. A  B = B  A at =0 or =180
B. R x  R y at =45
C. A dimensionless quantity may have a unit
D. When a scalar is multiplied with a vector then a scalar can be
produced
14. The tension in the string of a simple pendulum is:
A. Constant B. Maximum in the extreme position
C. Zero in the mean position D. None of the above
15. A diffraction pattern is obtained using a beam of red light. If the
red light is replaced by blue light, then:
A. The diffraction pattern remains unchanged
B. Diffraction bands become narrower and croweded together
C. Bands become broader and farther apart
D. Bands disappear
16. Point charge 4q, -2q, +q and -3q are placed at the corners of a
square of side a as shown in Fig. the potential at point O is:
A B

a
O

D C
a
1  10q 
A. Zero B.  
4 0  a 
1  2 2q  1  5q 
C.   D.  
4 0  a  4 0  a 

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17. Two gases A and B having the same temperature T, same pressure
P and same volume V are mixed. If the mixture is at the same
temperature T and occupies a volume V, the pressure of the
mixture is:
A. 2P B. P
C. P/2 D. 4P
18. c p − cv = .....
A.T B. K
C.R D. 2R
19. A uniform wire of length 5 m is carrying a steady current. The
electric field inside it is 0.2 V/m. The potential difference across the
ends of the wire is:
A. 1 volt B. 0.5 volt
C. 1.5 volt D. 5 volt
20. In the figure below, a fuse in one of the bulbs causes all the other to go
out. Which bulb has fused?

1 2 3

4 5

A. 1 B. 2
C. 3 D. 4
21. An electric bulb is rated 220 volts and 100 watts power consumed
by it when operated on 110 volts is:
A. 50 watts B. 75 watts
C. 90 watts D. 25 wattts
22. A magnetic needle is kept in a uniform magnetic field. It
experiences:
A. A force and a torque B. A force but not a torque
C. A torque but not a force D. Neither a torque nor a force
23. A lift is going up. The variation in the speed of the lift is as given in
the graph:
v
Velocity (m/sec)

3.6

t
2 10 12
What is the height to which the lift takes the passengers:
A. 3.6 meters
B. 28.8 meters
C. 36.0 meters
D. Cannot be calculated from the above graph

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24. A choke coil has negligible resistance. The alternating potential

difference across it is 220 volts and the current is 5 mA. The power
consumed is:
5 220
A. 220  watts B. watts
1000 5
C. Zero D. 220  5watts
25. For a ductile substance
A. It has elastic as well as plastic regions
B. It only has elastic region and breaks after it
C. It does not break just after elastic limit
D. Both “A” and “C”
26. Two wires of the same material have diameters in the ratio 2:1 and
lengths in the ratio 1:2. If they are stretched by the same force,
their elongations will be in the ratio
A. 8:1 B. 2:1
C. 1:8 D. 1:4
27. A conducting ring is placed around the core of an electromagnet as
shown in Fig. when key k is pressed, the ring:
Core
Ring

A. Remains stationary
B. Is attracted towards the electromagnet
C. Jumps out of the core
D. None of these
28. In a common base transistor circuit, the current gain is 0.98. On
changing emitter current by 5.00 mA, the change in collector
current is:
A. 0.196 mA B. 2.45 mA
C. 4.9 mA D. 5.1 mA
29. The maximum and minimum distances between a convex lens and
an object, for the magnification of a real image to be greater than
one, are:
A. 2f and f B. f and zero
C.  and 2f D. 4f and 2f
30. In a stationary wave, all the particles:
A. In the region between two antinodes birate in same phase
B. Of the medium vibrate in the same phase
C. On either side of a node vibrate in same phase
D. In the region between two nodes bibrate in same phase

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ANSWER KEY (Worksheet-39) 5. Answer is “C”

1 B 11 A 21 D Solution:- W = K.E so if W  0 ,
2 A 12 D 22 C energy must change.
3 C 13 D 23 C 6. Answer is “C”
4 C 14 D 24 C Solution:- when A.C is applied in X-rays
5 C 15 B 25 D tube as accelerating voltage is only
accelerate electrons towards anode during
6 C 16 A 26 C
+ve half cycle.
7 D 17 A 27 C
7. Answer is “D”
8 A 18 C 28 C
Solution:- from the equation of voltage;
9 A 19 A 29 A
V=10-2(x) ,as “x” increase “v” decrease
10 A 20 A 30 D
and its’s P.E must increase.
SOLUTIONS 8. Answer is “A”
Solution:- s=m so each term must be
Full Book (WS-39) m
1. Answer is “B” distance so; ct 2 = m  c = 2 .
s
Solution:- As both trains have similar 9. Answer is “A”
lengths, i-e, x1=x2=x so they cross each
Solution:- v f = 0ms −1 so all K.E is lost.
other means;
S=x+x=2x, vr=10+15=25ms-1 10. Answer is “A”
s Solution:- v = 1rev / s , r=20Km , ac = ?
vr =  s = vr  t = 25  4 = 100m
t v2 (2 ) 2
ac = 2 = = 8  5ms −2
100 r 20 10 3
2 x = 100m  x = = 50m
2 11. Answer is “A”
2. Answer is “A” Solution:-  when “v” increase “p”
Solution:- highest frequency means decreses.
maximum energy and also abosrtion 12. Answer is “D”
means from lower to highest orbit so but Solution:- H=20m but liquid height =H/4
option is A We must rember that R=max for hole of
3. Answer is “C” H
H
Solution:- For orbit transtion, we use the half of depth i-e , H  H  = 4 =
2 8
Lyman series;
13. Answer is “D”
1 l l 
= RH  2 − 2  ; n = 2,3, 4,5...... Solution:- a scalar cannot coverts a vector
 1 n  into scalar
Use this relation to find “  ” and then ““  2” 14. Answer is “D”
4. Answer is “C” Solution:- T=max at mean and T=min at
Solution:- whenever couple act on a body extreme
A) F = 0 15. Answer is “B”
Solution:- band-with   , so as blue has
B )  = 0 smallest “  ” so bandwidth will decrease and
C ) F = 0,  = 0 bands becomes crowded.

D) F = 0,   0

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16. Answer is “A” l1 A1 1 1 1

=  =  =
Solution:- At “O” W / q  is zero so V=0 l2 A2 2 4 8
17. Answer is “A”
Solution:-  v = same , so it means 27. Answer is “C”
malecules per unit volume must be doubled Solution:- when key is closed e..m.f is
so pressure must be doubled. include in ring and due to lenz’s law it
18. Answer is “C” moves upward.
28. Answer is “C”
Solution:- c p − cv = R I
19. Answer is “A” Solution:- current gain = c  I c
IB
Solution:- r = 5m, E = 0.2 vm −1 , v = ?
= curren gain = I B
v
E =  v = E r = 5  0.5 = 1volt =0.98x5mA
r =4.9mA
20. Answer is “A” 29. Answer is “A”
Solution:-only bulb-1 if goes off will cut Solution:- for M>1 we must place object
current of the circuit. b/w F and 2F.
21. Answer is “D” 30. Answer is “D”
V2 Solution:- Basic characertistic of
Solution:-  P = 2 (R=same)
R stationary waves.
V P 100
V  = so P = = = 25watt
2 2 4
22. Answer is “C”
Solution:- it ecxperience a couple and in a
cuople,  F = 0 but   0
23. Answer is “C”
Solution:- simply find total area under
the v-t curve.
24. Answer is “C”
Solution:- an inductor consumes no
pressure,  = 90 so
P = IV cos e = IV cos e90 = 0
25. Answer is “D”
Solution:- simple properties of a ductile
substance.
26. Answer is “C”
Solution:- as material is same so Y1=Y2
D1 r1 2
= =
D2 r2 1
2
A1  r1  4 l 1
=   = , 1 = , F1 = F2 so
A2  r2  1 l2 2
F l F l x
Y =   x =   1
A x r A x2

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