### Physics - Work, Energy and Power

#### Question - 1

A metre -strick of mass 200 g stands vertical on the ground .Work done to the make it lie horizontal on the ground is

• A zero
• B 0.2J
• C 1.96J
• D 0.98J

#### Question - 2

A body of mass 2 kg moves linearly at the speed of 10 ms-1 .A force F is applied on it due to which it moves with a speed of 20 ms-1 ,after covering a distance 3m .The magnitude of F is

• A 100 N
• B 10N
• C 33.3 N
• D 19.6 N

#### Question - 3

A mettalicsphere and a football with a same kinetic enregy are brought to rest by the application of the same retarding force.Assume no friction between the surfaces

• A The football will come to rest in a shorter time
• B The sphere will come to rest in a shorter time
• C Both will come to rest in a shorter time
• D Sphere will cover shorter distance

#### Question - 4

Consider a one-dimensional elastic collision between an incomming body P of mass m1 and another body Q  of mass m2 initially at rest .for body Q to move with the greatest kinetic energy after the collision

• A m1>m2
• B m1<m2
• C m1=m2
• D the body P must recoil back

#### Question - 5

A body of mass 1 kg falls from a height 1 m on the ground and it strikes the ground after time t.The momentum of the body is

• A 2g
• B $2\sqrt g$
• C $\sqrt{2g}$
• D $\sqrt g$

#### Question - 6

A collision is said to be elastic if

• A elastic bodies collide
• B inelastic bodies collide
• C total linear momentum is conserved
• D total energy before and after the collision remains the same

#### Question - 7

A body of mass 8 kg at rest is situated at 20 m from the ground.If it is released till its kinetic energy becomes equal to potential energy ,its velocity at that instant would be

• A 14 ms-1
• B 9.8 ms-1
• C 196 ms-1
• D 392 ms-1

#### Question - 8

For a body falling freely ,the ratio between potential enegy (P) and kinetic energy (K) at a given instant is 5:1 .When the velocity of the body increases by 100% ,the ratio $P\over K$ at that instant is

• A 1:1
• B 1:2
• C 1:5
• D 2:1

#### Question - 9

In an elastic collision

• A velocity always remains constant
• B linear momentum of each particle remains constant
• C loss in kinetic enregy equals the amount of workdone
• D total kinetic energy of the particles comprising the system remains constant

#### Question - 10

Law of conservation of linear momentum is applicable even in those cases where

• A Newton's first law of motion does not hold good
• B Newton's second law of motion does not hold good
• C Newton's third law of motion does not hold good
• D None of these