Physics problem using Newton's laws how to solve?

In summary, the conversation is about a physics problem involving two masses connected by a cord on inclined planes. The questions are about the net acceleration of the system, the string tension, and the weight of one mass needed for the system to move at a constant speed. The provided image shows the attempt at a solution, but the top two lines are unreadable.
  • #1
ax308
2
0

Homework Statement



how do i solve it ? if someone can help I will appreciate it.

Two masses m1 = m2 = 3 Kg and 5 Kg lie on two inclined planes with negligible friction connected via a cord that is inextensible and massless. The planes have angles of 30 degrees for m1 and 40 degrees for m2.
a) The net acceleration of the system ?
b) The string tension?
c) How much should m2 weigh for the masses to move to the right with constant speed?

this is the image
https://dl.dropbox.com/u/83441690/prb1.png

Homework Equations





The Attempt at a Solution


https://dl.dropbox.com/u/83441690/Photo%20Oct%2031%2C%207%2053%2020%20PM.jpg
 
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  • #2
I can't read the solution. Could you please type it out?
 
  • #3
sorry https://dl.dropbox.com/u/83441690/Photo%20Oct%2031%2C%209%2029%2050%20PM.jpg [Broken]
 
Last edited by a moderator:
  • #4
What do the top two lines say?
 
  • #5


First, we need to draw a free body diagram for each mass. For m1, there is a normal force acting perpendicular to the inclined plane, a weight force acting downward, and a tension force acting upward along the string. For m2, there is also a normal force, weight force, and tension force, but the normal and weight forces are at different angles due to the different angle of the inclined plane.

Next, we can apply Newton's second law, F=ma, to both masses. In the x-direction, the tension force is the only force acting, so we can set it equal to the mass times the acceleration in the x-direction. In the y-direction, we can use the weight and normal forces to calculate the net force in the y-direction and set it equal to the mass times the acceleration in the y-direction.

For part a), we can use the acceleration in the x-direction to find the net acceleration of the system. We can also use the same method to find the tension in the string for part b).

For part c), we can use the acceleration in the x-direction to calculate the weight of m2 needed for the system to move with constant speed to the right. We can set the tension force equal to the weight force of m2 and solve for the mass.

Overall, the key to solving this problem is to draw a clear free body diagram for each mass and apply Newton's second law to find the net acceleration and tension in the string.
 

1. What are Newton's laws of motion?

Newton's laws of motion are three fundamental principles that describe the behavior of objects in motion. The first law states that an object at rest will remain at rest, and an object in motion will continue in motion with constant velocity, unless acted upon by an external force. The second law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. The third law states that for every action, there is an equal and opposite reaction.

2. How do I apply Newton's laws to solve a physics problem?

To apply Newton's laws to solve a physics problem, you need to first identify the forces acting on the object and their direction. Then, use the second law (F=ma) to calculate the net force acting on the object. Finally, use the first law (F=ma) to determine the acceleration of the object. Repeat this process for each object in the problem, and then use the third law to determine how the objects interact with each other.

3. What is the difference between static and dynamic equilibrium?

Static equilibrium occurs when an object is at rest, or when it is moving at a constant velocity with no net force acting on it. Dynamic equilibrium occurs when an object is moving at a constant velocity with a net force acting on it, but the forces are balanced and cancel each other out. In both cases, the object's acceleration is zero, but in static equilibrium, there is no net force acting on the object, while in dynamic equilibrium, there is a net force but it is balanced.

4. Can Newton's laws be applied to non-inertial reference frames?

No, Newton's laws can only be applied to inertial reference frames, which are frames of reference that are not accelerating. In non-inertial reference frames, apparent forces such as centrifugal and Coriolis forces are present, which can complicate the application of Newton's laws.

5. What are some common misconceptions about Newton's laws?

One common misconception is that an object needs a force to stay in motion. In reality, an object in motion will continue in motion with constant velocity unless acted upon by an external force. Another misconception is that an object's mass and weight are the same. Mass is a measure of the amount of matter in an object, while weight is a measure of the force of gravity acting on an object. Finally, Newton's laws only apply to point masses, and not to extended objects with a size and shape.

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