Laws of Motion

Question 489
CBSEENPH11020382

A block of mass 0.50 kg is moving with a speed of 2.00 m/s on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

  • 0.16 J

  • 1.00 J

  • 0.67 J

  • 0.34 J

Solution

C.

0.67 J

m1u1 + m2u2 = (m1 + m2)v
v = 2/3 m/s
Energy space loss space equals space 1 half space left parenthesis 0.5 right parenthesis space straight x space left parenthesis 2 right parenthesis squared space minus space 1 half space left parenthesis 1.5 right parenthesis space straight x space open parentheses 2 over 3 close parentheses squared
space equals space 0.67 space straight J

Question 490
CBSEENPH11020392

A block of mass ‘m’ is connected to another block of mass ‘M’ by a spring (mass less) of spring constant ‘k’. The blocks are kept on a smooth horizontal plane. Initially the blocks are at rest and the spring is stretched. Then a constant force ‘F’ starts acting on the block of mass ‘M’ to pull it. Find the force on the block of mass ‘m’.

  • mF/M

  • (M+m)F/m

  • mF/(m+ M)

  • MF (m+M)

Solution

C.

mF/(m+ M)

Question 491
CBSEENPH11020401

A particle is projected at 60° to the horizontal with a kinetic energy K. The kinetic energy at the highest point is 

  • K

  • 0

  • K/2

  • K/4

Solution

D.

K/4

Question 492
CBSEENPH11020406

A bomb of mass 16 kg at rest explodes into two pieces of masses of 4 kg and 12 kg. The velocity of the 12 kg mass is 4 ms−1 . The kinetic energy of the other mass is

  • 144 J

  • 96 J

  • 288 J

  • 192 J

Solution

C.

288 J

m1v1 = m2v2
KE space equals space 1 half straight m subscript 2 straight v subscript 2 superscript 2 space
space equals space 1 half space straight x space 4 space straight x space 144 space equals space 288 space straight J

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