# Two 4 kg blocks hang from a rope

Get a free answer to a quick problem. Most questions answered within 4 hours. Choose an expert and meet online. No packages or subscriptions, pay only for the time you need. A light block of mass m and a heavy block of mass M are attached to the ends of a rope.

## Two masses are connected with a rope and pulley...

A student holds the heavier block and lets the lighter block hang below it. Then she lets go. Air resistance can be neglected. What is the tension in the rope while the blocks are falling, before either hits the ground? Would your answer be different if she had been holding the lighter block initially?

Add comment. Hi Essie! One great aspect of Newton's 2nd law, among many, is that we get to define the "system" that we are working with. Newton's 2nd law tells us that the net external force on the system equals the system's mass times its acceleration. But we can make the system whatever we want. Only forces outside our system affect acceleration this fact can be explained via Newton's third law, but we need not do that at the moment. For this case, let's start by wrapping our "system bubble" around both masses.

Then, any tension in the rope between them would be internal, inside the system, and we need not include it in our Newton's 2nd law expression. The only force external to our system that we care about in that case is gravity. Thus, Newton's 2nd law becomes:.Hot Threads. Featured Threads. Log in Register. Search titles only.

## Newton's Third Law Problem: Two masses, a rope and a pulley

JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding. Newton's Third Law Problem: Two masses, a rope and a pulley. Thread starter Zeke Bevan Start date Oct 16, Tags newtons laws of motion newtons third law newtons third law of motion'. Zeke Bevan. Homework Statement Two blocks are attached to opposite ends of a massless rope that goes over a massless, frictionless, stationary pulley.

What is the mass of the other block? Homework Equations There were no given equations. I'm confused because I'm assuming there isn't an angle and I don't know wether to include tension in this problem or not. This chapter has been really hard for me setting up problems. Homework Helper. Insights Author. Gold Member. Zeke Bevan said:. I'm assuming there isn't an angle.

### Problem: Two masses on a pulley

I don't know wether to include tension in this problem. So, the forces acting on each block is gravity pulling the blocks down and tension in the rope holding the blocks together? If there is tension in the rope, can I assume there are equal to each other as well? I'm really sorry if am oblivious on how to do this problem, I'm finding myself to be not good at physics but I really wish to be. You are given that the rope is massless and that the pulley is massless and frictionless.

This has implications for the tension in the rope. For instance, if the tension at two ends of a length of massless rope were different, what acceleration would result? I can only think that the accelerations would be different? One object would be pull down while the other got pulled up. What is the acceleration of the rope if the tension at the two ends are different? For a massless string or rope, the tension will be the same throughout its length, yes.Hot Threads. A second rope hangs beneath the lower block. Both ropes have a mass of g. The entire assembly is accelerated upward at by force. What is F? What is the tension at the top end of rope 1? What is the tension at the bottom end of rope 1? What is the tension at the top end of rope 2? Thank you. Doc Al Mentor. To find F, consider the masses and ropes as a single system. What external forces act on the system? What's the acceleration? Now what?? StephenDoty said:. If we make it one system the external forces are: F and weight of the blocks.

You must log in or register to reply here. Last Post Oct 9, Get a free answer to a quick problem. Most questions answered within 4 hours. Choose an expert and meet online. No packages or subscriptions, pay only for the time you need. Two masses are connected with a rope and pulley as shown:. If the mass on the ramp is m1 and the hanging mass is m2 carefully complete the free-body diagram for the system.

Be sure that forces include the subscript "1" if they are associated with mass 1 and "2" if they are associated with mass 2. Assume frictionless for now. What forces or components of forces must we compare to determine if the box on the ramp goes up or down?

Identify these forces below then circle these forces on the free-body diagram. Show any calculations below. Add comment. Unfortunately this part does not allow diagram or drawing. Assuming the system is static i. If frictional force is present, this force is always against the motion. For example, if the objects move down the ramp then the frictional force is up the ramp. So after solving b we know which direction are the objects moving we can then know the direction of the frictional force. Where a is the acceleration 60 — 45 — 5. Ask a question for free Get a free answer to a quick problem. Find an Online Tutor Now Choose an expert and meet online.You can assume that the rope is massless and inextensible, and that the pulley is frictionless. Find the upward acceleration of the smaller mass and the tension in the rope. We have a massless rope that runs over a frictionless pulley, this means that the two masses are subject to upward tensions equal in magnitude.

We will indicate the magnitude of the tensions with T. In the case of the smaller mass, the tension wins the force of gravity, which means that the smaller mass is accelerating upward. However, in the case of the larger mass, the force of gravity wins the tension, which means that the larger mass is accelerating downward.

Also, since the rope is inextensible, the two masses move with accelerations that are equal in magnitude. We will indicate the magnitude of the accelerations with a. Here are the free-body diagrams of the two masses:. We want to find the acceleration of the smaller mass which, as we saw has the same magnitude as the acceleration of the larger massand the tension in the rope. The smaller mass is subject to two forces: T directed upward and m g directed downwardwhere T is larger in magnitude.

Therefore, the resultant force r will be directed upward, and have the magnitude equal to the difference between T and m g :. The larger mass is also subject to two forces: T directed upward and M g directed downwardwhere M g is larger in magnitude.

Therefore, the resultant force R will be directed downward, and have the magnitude equal to the difference between M g and T :. We now have two equations with 3 unknowns: rRT.

We can reduce the number of unknowns to 2 by remembering that the two masses have accelerations equal in magnitude. Indeed, applying Newton's 2 nd Lawthe magnitudes of the two resultant forces can be expressed as:. So, we can substitute r and R in Eq. We now have two equations with 2 unknowns a and Tso we can solve them.

Physics - Pulley System on a Table (1 of 2) Frictionless Table

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### Physics question?

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PillPack Pharmacy Simplified. Amazon Renewed Like-new products you can trust. Amazon Second Chance Pass it on, trade it in, give it a second life.Two blocks are connected by a rope that passes over a set of pulleys.

One block has a weight of N, and the other has a weight of N. The rope and the pulleys are massless and there is no friction. As part a of the drawing shows, two blocks are connected by a rope that passes over a set of pulleys. When released, what is the acceleration of the larger block?

What is the tension in the rope? A is connected to a rope that. Blocks A, B, and C are placed as in the figure and connected by ropes of negligible mass. Both A and B weigh Block C descends with constant velocity. Find the. Problem 3- Blocks A, B, and C are connected by ropes and placed as in the figure. Two blocks are connected by a rope that passes over a massless and frictionless pulley as shown in the figure below. The two blocks in the figure are connected by a massless rope that passes over a pulley.

The pulley is 17 in diameter and has a mass of 1. As the pulley turns, friction at the axle exerts a torque of magnitude 0. If the blocks are released from. The pulley is 12 cm in diameter and has a mass of 2. Two blocks are connected by a massless rope that passes over a pulley. The pulley is 12cm in diameter and has a mass of 2kg. Three blocks of masses 8. The acceleration of the 5. The acceleration of. 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 masses of blocks A and B are 4. The blocks are initially at rest and are connected by a massless string passing over a massless, frictionless pulley.

The system is released from rest. What is the acceleration of the. These blocks are further connected to a block of mass 3kg by another light string that passes overr a pully of negligible mass and friction. Blocks 1 and.