# Help Me Two Blocks Connected by a Cord

• awesome4444
In summary, the two blocks move with an acceleration equal to the mass of the block being moved divided by the mass of the block being moved (in this case it is just the mass of block A).

#### awesome4444

Mechanics help :(!

I REALLY NEED HELP :(
Two blocks are connected by a cord which passes over a frictionless pulley at D.
Block A has a mass of 40 kg and block B a
mass of 120 kg. A rests on a horizontal
surface, while B rests on a ramp with the slope
shown. B is initially in a position 3 m from the
stop C as shown. The coefficient of kinetic
friction between the blocks and the surface
beneath is μK = 0.20 for both A and B.

(a) Find the acceleration of the two blocks and
the tension T in the cord, assuming that the
blocks just begin to move at time t = 0.

Diagram?

First we draw the FBD for mass A and for mass B.

How many forces act on each?

on mass 1 we have forcetension - forcefriction + m*g = ma
mass2 -frocetension-Forcefriction2+(m*g)sin theta= m2a

the thing that's confusing me is if we could have assumed that the aceleration of B is same as acceleration of a before it hits the barrier in the diagram

awesome4444 said:
on mass 1 we have forcetension - forcefriction + m*g = ma
mass2 -frocetension-Forcefriction2+(m*g)sin theta= m2a

the thing that's confusing me is if we could have assumed that the aceleration of B is same as acceleration of a before it hits the barrier in the diagram

To avoid confusion, instead of mass 1 let us call it mass A as in diagram.

Re 1st equation: I do not know why you have m*g.

Until mass B hits the barrier at C we HAVE TO assume that the acceleration of B is the same (in magnitude) as that of A because otherwise the string either snaps or becomes slack and so there would not be any tension at all!

## 1. What is the purpose of connecting two blocks with a cord?

The purpose of connecting two blocks with a cord is to demonstrate the concept of tension in physics. The cord represents a force being applied to the blocks, causing them to be pulled towards each other. This force is known as tension, and it is an important concept in understanding the mechanics of objects connected by cords or ropes.

## 2. How does the tension in the cord affect the blocks?

The tension in the cord affects the blocks by pulling them towards each other. This is known as a compressive force, as the blocks are being pushed together. The amount of tension in the cord can also affect the motion of the blocks, as a greater tension will result in a greater force being applied to the blocks.

## 3. What factors can affect the tension in the cord?

The tension in the cord can be affected by several factors, including the length and thickness of the cord, the weight of the blocks, and the angle at which the cord is pulled. The type of material the cord is made of can also impact the tension, as some materials are more elastic and can stretch more than others.

## 4. How is tension related to other forces in the system?

Tension is a type of force, and as such, it is related to other forces in the system. In the case of two blocks connected by a cord, tension is balanced by the force of gravity pulling the blocks downwards. Other external forces, such as friction and air resistance, can also affect the tension in the cord and the motion of the blocks.

## 5. What real-life applications can be demonstrated by the "Help Me Two Blocks Connected by a Cord" experiment?

The "Help Me Two Blocks Connected by a Cord" experiment can demonstrate several real-life applications, including how cranes and pulley systems work, how bridges and suspension structures are designed, and the concept of tension in bungee jumping and rock climbing. It can also help students understand the physics behind everyday objects, such as elevators and ziplines.