Newton's second law problem

In summary, the conversation discusses a problem involving a triangle-shaped moving block and a block on top of it. The first question is about finding the force needed for the triangle block to stay at rest. The second question involves finding the acceleration of the top block in order for the triangle block to move up on it with a specific acceleration. The third question is similar, but with the triangle block moving down. The conversation also mentions using the equivalence principle and D'Alembert's principle to solve the problem. The conversation ends with a request for further help and thanking the other person for their assistance.
  • #1
Dweirdo
174
0

Homework Statement


A triangle shaped moving block of mass M2 is pushed by force F , a block of mass M1 is on the other block, a)what should be the F force so that the block will be in rest relative to M2?
b)what should be the Acceleration of M1 so that the block M2 will move up on the block M1 in an acceleration of A2?
c)what should be the Acceleration of M1 so that the block M2 will move down on the block M1 in an acceleration of A2?

Homework Equations


F=ma... etc
equivalence principle can help here as well...

The Attempt at a Solution


K, a) is done for me, easy, solved it in two ways 1)equivalence principle(elegant way),
2)using D'Alembert's principle and some Newton's laws.

now b) ffs! I hate it, nothing that I do works! nothing that I could think off,damnit!
the main thing that bothers me is that they don;t have the same acceleration now!

So If some 1 can point me in the right direction/hints or W\E that will help me finish this problem.
this is an epic sketch> I will add a normal one if it is needed.
| \
| \
| \M2
|M1\ pushed to the right-------->>>

so thank You!
 
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  • #2
I think we need that in monospace :smile:
Code:
| \
|  \
|   \M2
|M1  \       pushed to the right-------->>>

Anyway: the straightforward way is probably just plain old free-body diagrams. You know the force on the smaller block has to be [tex]m_2 a_2[/tex] directed upward and to the left, so just draw the diagram and instead of making the forces balance, let there be a difference of [tex]m_2 a_2[/tex] in that upward direction. Then I guess you could figure out what the excess force on the larger block is and divide by its mass to get its acceleration.

Alternatively, since you mentioned D'Alembert's principle: if you're familiar with the Euler-Lagrange equation, you could try using that with the displacement of the smaller block along the ramp as one generalized coordinate. I'm not sure offhand whether this or the free-body diagrams would be easier to work out.
 
  • #3
"if you're familiar with the Euler-Lagrange equation"
Nope,Haven't studied it yet :<
do the bodies have the same acceleration in the X direction(right direction)??
 
  • #4
OK It's done, thank You for your hep.
but there are more questions on this problem , ill write them later :D
so thanks
 

1. What is Newton's second law?

Newton's second law states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportional to its mass. In simpler terms, the larger the force applied to an object, the greater its acceleration will be, and the more massive the object, the slower its acceleration will be.

2. How is Newton's second law used to solve problems?

To solve problems involving Newton's second law, you can use the formula F=ma, where F is the net force, m is the mass of the object, and a is the acceleration. By plugging in known values and solving for the unknown, you can determine the force, mass, or acceleration of an object.

3. What is the difference between mass and weight?

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. Mass is measured in kilograms (kg) and is constant, while weight is measured in newtons (N) and can vary depending on the strength of gravity.

4. Can Newton's second law be applied to objects in free fall?

Yes, Newton's second law can be applied to objects in free fall. In this case, the net force acting on the object is its weight (mg), and the acceleration is the acceleration due to gravity (g). Therefore, the formula becomes F=mg, and you can solve for the object's weight or mass.

5. What are some real-life examples of Newton's second law in action?

Some examples of Newton's second law in action include a car accelerating when the gas pedal is pressed, a balloon being pushed by air as it is released, and a rocket being propelled into space by the force of its engines. It is also evident in everyday actions, such as throwing a ball or riding a bike.

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