Free help with homework

Why join Brainly?

  • ask questions about your assignment
  • get answers with explanations
  • find similar questions

1. Two bodies of mass 3 kg and 4 kg are suspended at the ends of massless string passing over a

frictionless pulley. The acceleration of the system is (Take g = 9.8 m/s2)

2.A ball of mass 100 g and another ball of 120 g moves towards each other with speeds 6 m/s
and 5 m/s respectively. If they stick to each other colliding, what would be the velocity of the
combined mass after the collision?




This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
The mass of 3 kg goes up  and  mass of 4 kg comes down with an acceleration a.  The tension in the string is uniform through out its length and is T.

     T - 3 * g = 3 * a
     4 * g - T = 4 * a
   solving these,  a = g/7 = 1.4 m/sec/sec   and    T = 24 * 1.4 Newtons

       Inelastic collision. 
   momentum is conserved after collision.  There is a loss of energy in collision.

     100 * 6 - 120 * 5 = (100+120) * v
           v = 0          =>    the combined mass becomes stationary.

1 5 1
cant understand
1st question. tension - weight of 3kg = mass 3kg * acceleration.... weight of 4 kg - tension in string = mass 4 kg * acceleration .. since the string is tight, does not expand on pulling, the acceleration of 3 kg and 4 kg are same.. entire string moves at same speed at every instant.
sum of initial momentum of both = 100 gm * (+6 m/s) + 120 gms * (-5 m/s) = 0. we use -5 m/s as it is in - x direction when 6 m/s is in +x direction. Hence on adding the two vectors (momentum), net momentum is zero.
there is energy loss = 1/2 m1 v1^2 + 1/2 m2 v2^2. due to inelastic collision. this energy is dissipated as sound, heat and light. also the bodies get deformed in shape. the energy is used in changing the shape of bodies.
The Brain
  • The Brain
  • Helper
Not sure about the answer?
Learn more with Brainly!
Having trouble with your homework?
Get free help!
  • 80% of questions are answered in under 10 minutes
  • Answers come with explanations, so that you can learn
  • Answer quality is ensured by our experts