IIT JEE MCQ Quiz Hub

1. A load suspended by a massless spring produces an extension of x cm in equilibrium. When it is cut into two unequal parts the same load produces an extension of 7.5 cm when suspended by the large part of length 60 cm. When it is suspended by the smaller part the extension is 5.0 cm. then:
x = 12.5
x = 3.0
the length of the original spring is 90 cm
the length of the original spring is 80 cm

2. A force F is needed to break a copper wire having radius R. The force needed to break a copper wire of same length and radius 2R will be
F / 2
2F
4F
F / 4

3. When a weight of 5 kg is suspended from a copper wire of length 30 m and radius 0.5 mm the length of the wire increases by 2.4 cm. If the radius is doubled the extension produced is:
1.2 cm
0.6 cm
0.3 cm
0.15 cm

4. For gases:
isothermal elasticity is greater than adiabatic elasticity
adiabatic elasticity is greater than isothermal elasticity
both the elasticities are equal
none of the above

5. On what factor should the coefficient of restitution depend when two bodies having masses m and M (m < M) collide with each other?
Coefficient of restitution depends upon Youngs modulus of elasticity of heavier body only
Coefficient of restitution depends upon Youngs modulus of elasticity of lighter body only
Coefficient of restitution depends upon Youngs modulus of elasticity of both the bodies
Coefficient of restitution depends upon Nature of collision (wheather it is head on or oblique)

6. A wire suspended vertically from one of its ends is stretched by attaching a weight of 200 N to the lower end. The weight stretches the wire by 1 mm. Then the elastic energy stored in the wire is:
0.2 J
10 J
20 J
0.1 J

7. Youngs modulus is defined for:
solid
liquid
gas
all of these

8. The longitudinal extension of any elastic material is very small. In order to have an appreciable change the material must be in the form of:
thin block of any cross-section
thick block of any cross-section
long thin wire
short thin wire

9. Youngs modulus for perfectly inelastic body is:
finite
one
zero
infinity

10. Which of the following substances has the highest value of the Youngs modulus?
Steel
Rubber
Wood
Plastic

11. A wire is stretched 1 mm by a force of 1 kN. How far would a wire of the same material and length but of four times that diameter be stretched by the same force ?
1 / 2 mm
1 / 4 mm
1 / 8 mm
1 / 16 mm

12. When a rubber cord is stretched the change in volume with respect to change in its linear dimensions is negligible. The Poisson s ratio for rubber is
1
0.25
0.5
0.75

13. When a certain weight is suspended from a long uniform wire its length increases by one cm. If the same weight is suspended from another wire of the same material and length but having a diameter half of the first one the increase in length will be
0.5 cm
2 cm
4 cm
8 cm

14. Four wires of the same material are stretched by the same load. The dimensions of the wires are as given below. The one which has the maximum elongation is of:
diameter 1 mm and length 1 m
diameter 2 mm and length 2 m
diameter 0.5 mm and length 0.5 m
diameter 3 mm and length 3 m

15. When the intermolecular distance decreases due to compressive force there is:
zero resultant force between molecules
repulsive force between molecules
attractive force between molecules
no force between molecules

16. A string 1 mm in diameter breaks if the tension in it exceeds 80 N. The maximum tension that may be given to a similar string of diameter 2 mm is
40 N
80 N
320 N
1640 N

17. A wire elongates by l mm when a load w is hanged from it. If the wire goes over a pulley and two weights w each are hung at the two ends the elongation of the wire will be (in mm):
1
21
zero
1/2.

18. A wire can sustain a weight of 10 kg before breaking. If the wire is cut into two equal parts then each part can sustain a weight of
2.5 kg
5 kg
10 kg
15 kg

19. The length of an elastic string is a metre when the tension is 4 N and b metre when the tension is 5 N. The length in metres when the tension is 9 N is:
4a ? 5b
5b ? 4a
9b ? 9a
a + b

20. A spring of constant K is cut into parts of length in the ration 1 : 2. The spring constant of larger one is
K / 2
K / 3
2K / 3
3K / 2

21. Two bars A and B of circular cross-section and of same volume and made of the same material are subjected to tension. If the diameter of A is half that of B and if the force applied to both the rods is the same and it is in the elastic limit the ratio of extension of A to that of B will be842
16
8
4
1

22. What happen to the elastic property of a substance after annealing (cooling slowly after heating)?
Increases
Decreases
Remains as such
Becomes zero

23. Two wires of the same material and radius but having length in the ratio of 1 : 2 are stretched with the same force. The ratio of the work done in two cases is
1:02
2:01
1:03
1:08

24. Two wires of the same material and length are stretched by the same force. Their masses are in the ratio 3:2 their elongations are in the ratio:
3:02
9:04
2:03
4:09

25. The property due to which a material can be hammered into thin sheet is called:
ductility
malleability
brittleness
elasticity

26. The modulus of elasticity is dimensionally equivalent to:
surface tension
stress
strain
none of these

27. The Youngs modulus of a wire is numerically equal to the stress which will:
not change the length of the wire
double the length of the wire
increase the length by 50%
change the radius of the wire to half

28. If a metal wire of length L having area of cross-section A and Youngs modulus Y behaves as a spring of spring constant k. The value of k is:
YA/L
YA/2L
2YA/L
YL/A

29. You are given three wires A B and C of the same length and cross-section. They are each stretched by applying the same force to the ends. The wire A is stretched least and comes back to its original length when the stretching force is removed. The wire B is stretched more than A and also comes back to its original length when the stretching force is removed. The wire C is stretched most and remains stretched even when stretching force is removed. The greatest Young s modulus of elasticity is possessed by the material of wireABC
A
B
C
Data is not sufficient

30. The length of a wire is increased by 1 mm on the application of given load. In a wire of the same material but of length and radius twice that of the first on the application of the same load extension is4 mm
0.25 mm
0.5 mm
2 mm
1 mm

31. Two wires of the same length and same material but radii in the ratio of 1 : 2 are stretched by unequal forces to produce equal elongation. The ratio of the two forces is
1:01
1:02
1:03
1:04

32. The dimensions of four wire of the same material are given below. In which wire the increase in length will be maximum ?
Length 100 cm Diameter 1 mm
Length 200 cm Diameter 2 mm
Length 300 cm Diameter 3 mm
Length 50 cm Diameter 0.5 mm.

33. Two wires of the same material and length are stretched by the same force. Their masses are in the ratio 3 : 2. Their elongations are in the ratio
3:02
9:04
2:03
4:09

34. If the work done in stretching a wire by 1 mm is 2 J the work necessary for stretching another wire of same material but with double radius of cross-section and half the length by 1 mm is
1 / J
4 J
8 J
16 J

35. Two identical wires are suspended from the same rigid support but one is of copper and the other is of iron. Young s modulus of iron is thrice that of copper. The weights to be added on copper and iron wires so that the ends are on the same level must be in the ratio of
1:03
2:01
3:01
4:01

36. A uniform wire fixed at its upper end hangs vertically and supports a weight at its lower end. If its radius is r its length L and Young s modulus for the material of the wire is E the extension is (1) directly proportional to E(2) inversely proportional to r.(3) directly proportional to L
if 1 2 3 are correct
if 1 2 are correct
if 2 3 are correct
if 3 only is correct

37. A force F is required to break a wire or length l and radius r. What force is required to break a wire of the same material having twice the length and six times the radius ?
F
3 F
9 F
36 F

38. A cube of aluminium of sides 0.1 m is subjected to a shearing force of 100 N. The top face of the cube is displaced through 0.02 cm with respect to the bottom face. The shearing strain would be
0.02
0.1
0.005
0.002

39. The length of an elastic string is a metre when the tension is 4 N and b metre when the tension is 5 N. The length in metre when the tension is 9 N is
5b - 4a
4a - 5b
a + b
b - a

40. A 2 m long rod of radius 1 cm which is fixed from one end is given a twist of 0.8 radius. The shear strain developed will be
0.002
0.004
0.008
0.016

41. A helical spring extends 40 mm when stretched by a force of 10 N and for tensions up to this value the extension is proportional to the stretching force. Two such springs are joined end to-end and the double-length spring is stretched 40 mm beyond its natural length. The total strain energy in J stored in the double spring is
0.05
0.1
0.2
0.4

42. Three wires PQ and R of the same material and length have radii 0.1 cm 0.2 cm and 0.3 cm respectively. Which wire has the highest value of Young s modulus of elasticity ?PQR
P
Q
R
All have the same value

43. The increase in length on stretching a wire is 0.05%. If its Poisson s ratio is 0.4 the diameter is reduced by
0.01%
0.02%
0.03%
0.04%

44. A piece of copper wire has twice the radius of a piece of steel wire. The Young s modulus for steel is twice that for the copper. One end of the copper wire is joined to one end of the steel wire so that both can be subjected to the same longitudinal force. By what fraction of its length of the copper has increased by 1% ?
1%
2%
2.50%
3%

45. A wire of length L and radius r is clamped rigidly at one end. When the other end of the wire is pulled by a force F its length increases by l . Another wire of the same material of length 4 L and radius 4r is pulled by a force 4F. The increase in length will be
l / 2
l
2l
4l

46. A wire extends by 1 mm when a force is applied. Double the force is applied to another wire of same material and length but half the radius of cross-section. The elongation of the wire in mm will be
8
4
2
1

47. For a given material the Young s modulus is 2.4 times that of modulus of rigidity. Its Poisson s ratio is
0.1
0.2
0.3
0.4

48. Two wires of the same material and same are stretched by the same force. Their lengths are in the ratio 2 : 3. Their elongations are in the ratio
3:02
2:03
4:09
9:04

49. When a weight of 5 kg is suspended from a copper wire of length 30 m and diameter. 0.5 the length of the wire increases by 2.4 cm. If the diameter is doubled the extension produced is
1.2 cm
0.6 cm
0.3 cm
0.15 cm

50. When a 4 kg mass is hung vertically on a light spring that obeys Hooke s law the spring stretches by 2 cm. The work required to be done by an external agent in stretching this spring by 5 cm will be
4.9 J
2.45 J
0.495 J
0.245 J