A steel wire with cross-section 3 cm2 has elastic limit 2.4

Subject

Physics

Class

NEET Class 12

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.
Advertisement

 Multiple Choice QuestionsMultiple Choice Questions

1.

If the units of length, mass and force are chosen as fundamental units, the dimensions of time would be

  • [ M1/2 L-1/2 F1/2 ]

  • [ M1/2 L1/2 F1/2 ]

  • [ M1/2 L1/2 F-1/2 ]

  • [ M1/2 L-1/2 F-1/2 ]


2.

A block of mass 2 kg is placed on the floor. The coefficient of static friction is 0·4. If a force of 2·8 N is applied on the block parallel to the floor, the force of friction between the block and the floor is (g = 10 ms-2 )

  • 2·8 N

  • 2 N

  • 8 N

  • Zero


3.

A heavy truck moving with a velocity of 60 km h-1 collides with a light drum at rest. If the collision be elastic, then the velocity of the drum immediately after collision will be

  • zero

  • 60 km h-1

  • 120 km h-1

  • uncertain


4.

A cyclist is moving in a circular track of radius 80 m with a velocity of 36 km h-1. He has to lean from the vertical approximately through an angle (Take g = 10 m s-2 )

  • tan-1 (4)

  • tan-1(1/8)

  • tan-1(1/4)

  • tan-1(2)


Advertisement
5.

A satellite is in an orbit around the earth. If its kinetic energy is doubled, then

  • it will maintain its path

  • it will fall on the earth

  • it will rotate with a great speed

  • it will escape out of earth's gravitational field


Advertisement

6.

A steel wire with cross-section 3 cm2 has elastic limit 2.4 x 108 N m-2. The maximum upward acceleration that can be given to a 1200 kg elevator supported by this cable wire if the stress is not to exceed one-third of the elastic limit is (Take g = 10 ms-2)

  • 12 m s-2

  • 10 m s-2

  • 8 m s-2

  • 7 m s-2


B.

10 m s-2

Maximum tension an elevator can tolerate is

         T = 13 × stress × area of cross-section

            = 13 × ( 2·4 × 108 ) ×  ( 3 × 10-4)

         T = 2·4 ×  104 N

If a is the maximum uoward acceleration of elevator then

        T = m ( g + a )

    2·4 ×  104 = 1200 ( 10 + a )

⇒  10 + a = 20

⇒     a = 10 m s-2


Advertisement
7.

An arrow is projected into air. Its time of flight is 5 s and range 200 m. What is the maximum height reached by it? ( Take g= 10 ms-2 )

  • 31·25 m

  • 24·5 m

  • 18·25 m

  • 46·75 m


8.

A particle moves in a circular path with decreasing speed. Choose the correct statement.

  • Angular momentum remains constant

  • Acceleration α is towards the centre

  • Particle moves in a spiral path with decreasing radius

  • The direction of angular momentum remains constant


Advertisement
9.

A body of mass 2 kg is thrown up vertically with kinetic energy of 490 J. The height at which the kinetic energy of the body becomes half of its original value is

  • 50 m

  • 12.25 m

  • 25 m

  • 10 m


10.

Two homogeneous spheres A and B of masses m and 2m having radii 2a and a respectively are placed in touch. The distance of centre of mass from first sphere is

  • a

  • 2a

  • 3a

  • none of these


Advertisement