physics

posted by .

A light rope is attached to a block with a mass of 6 kg that rests on a horizontal, frictionless surface. THe horizontal rope passes over a frictionless, massless pulley, and a block of mass m is suspended from the other end. When the blocks are released, the tension in the rope is 18 N. a) what is the acceleration of the 6 kg block ? b) the mass m of the hanging block?

a) is 3 m/s
b) is 2.65 kg
I don't get the equations I should have used

Use Newton's second law:

F = m a

The tension of 18 N pulls on the 6 kg block, so it's acceleration is:

a = 18 N/(6 kg) = 3 m/s^2

Now the length of the rope can't change and it is pulled tight by the falling weight. This means that if the mass on the surface is accelerating at 3 m/s^2, the mass m is dropping downward with this acceleration.

The force on the hanging rope is (let's take the downward directon as positive):

F = m g - 18 N

But this has to equal m*a by Newton's second law and we know that a = 3 m/s^2.

m g - 18 N = m*(3 meters/s^2) --->

m = 18 N/[g - 3 m/s^2] = 2.64 kg

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. physics

    A light rope is attached to a block with a mass of 6 kg that rests on a horizontal, frictionless surface. THe horizontal rope passes over a frictionless, massless pulley, and a block of mass m is suspended from the other end. When …
  2. physics

    A block of mass M = 6.755 kg is pulled along a horizontal frictionless surface by a rope of mass m = 0.592 kg, as shown in Fig. 5-63. A horizontal force = 41.5 N is applied to one end of the rope. Assume that the rope only sags a negligible …
  3. Physics

    A block of mass m1 is on top of a block of mass m2. Block 2 is connected by an ideal rope passing through a pulley to a block of unknown mass m3 as shown. The pulley is massless and frictionless. There is friction between block 1 and …
  4. physics

    A light rope is attached to a block with a mass of 10 kg that rests on a horizontal, frictionless surface, and a block of mass, m, is suspended from the other end. The tension in the rope is 20 N when the blocks are released. a) What …
  5. Physics

    Block A sits on a horizontal tabletop. There is friction between the surface and Block A. The string passes over a frictionless, massless pulley. Block B hangs down vertically. When the two blocks are released, Block B accelerates …
  6. Physics

    Block A sits on a horizontal tabletop. There is friction between the surface and Block A. The string passes over a frictionless, massless pulley. Block B hangs down vertically. When the two blocks are released, Block B accelerates …
  7. Physics

    Block A (Mass = 3.146 kg) and Block B (Mass = 2.330 kg) are attached by a massless string Block A sits on a horizontal tabletop. There is friction between the surface and Block A. The string passes overa frictionless, massless pulley. …
  8. Physics

    Block A (Mass = 3.500 kg) and Block B (Mass = 2.450 kg) are attached by a massless string Block A sits on a horizontal tabletop. There is friction between the surface and Block A. The string passes overa frictionless, massless pulley. …
  9. PHYSICS, help!

    A 5 kg block rests on a frictionless horizontal surface. A cord attached to the block passes over the pulley whose diameter is 0.120 m to the hanging block of mass 5 kg. The system is released from rest and the blocks are observed …
  10. PHYSICS

    A 5 kg block rests on a frictionless horizontal surface. A cord attached to the block passes over the pulley whose diameter is 0.120 m to the hanging block of mass 5 kg. The system is released from rest and the blocks are observed …

More Similar Questions