Newton's Laws Applications - Systems

In summary: No, there's no difference between the magnitude of the tension in problem 1.As for the acceleration, in those problems, we are supposed to find:normal forcetensionaccelerationm\vec{g} = M\vec{a_M} + T\vec{v}m\vec{a_M} = Mg - T\vec{v} = Ma_MSo, for the second problem, add the force vectors to find the net force:\vec{F_M} = M\vec{g} + \vec{T} = M\vec{a_M} + \vec{v} = M\
  • #1
BillTheButcher
4
0
Hello,

I am taking intro Physics and we are having a little quiz this friday. Professor gave us handouts and told us to solve them by ourselves, and then study those problems because the same problems will be on the quiz. Now, my problem is, is that I really don't understand the subject, because professor just gives us these handouts and expects us to solve them by ourselves after a one minute quick explanation.

This handout has 12 problems, I know how to draw labels on them and do a free-body diagram... but I don't know how to do calculations... professor didn't help us do them, so I'm trapped in a paradox, I want to study for friday but have no material to study from. So, can you help me solve the CALCULATIONS (I know how to draw labels), so I can study and examine them by friday and not fail the quiz?

Since they are graphs and I can't draw here, I attached 5 well-visible images.

1st: http://img28.imageshack.us/img28/5849/nggw.jpg
2nd: http://img5.imageshack.us/img5/6608/81oz.jpg
3rd: http://img14.imageshack.us/img14/7445/xcup.jpg
4th: http://img30.imageshack.us/img30/5777/13x.JPG
5th: http://img35.imageshack.us/img35/8440/2uk.JPG

Here are my attempts but there's no chance they're correct:

1st: http://img849.imageshack.us/img849/6103/pxcq.jpg
2nd: http://img543.imageshack.us/img543/686/4r6u.jpg
 
Last edited by a moderator:
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  • #2
BillTheButcher said:
1st: http://img28.imageshack.us/img28/5849/nggw.jpg
2nd: http://img5.imageshack.us/img5/6608/81oz.jpg
3rd: http://img14.imageshack.us/img14/7445/xcup.jpg
4th: http://img30.imageshack.us/img30/5777/13x.JPG
5th: http://img35.imageshack.us/img35/8440/2uk.JPG

Here are my attempts but there's no chance they're correct:

1st: http://img849.imageshack.us/img849/6103/pxcq.jpg
2nd: http://img543.imageshack.us/img543/686/4r6u.jpg
For the first problem, is there any difference between the magnitude of the tension acting on m and of the tension acting on M?

How is the acceleration of M related to the acceleration of m?

Can you write the equations for the accelerations of m and M and for the relationship between their accelerations? That should give you 3 equations and 3 unknowns (am, aM, and T) which you can now solve.

AM
 
Last edited by a moderator:
  • #3
No, there's no difference between the magnitude of the tension in problem 1.

As for the acceleration, in those problems, we are supposed to find:
normal force
tension
acceleration

Masses will be given, as well as coefficient of friction (only kinetic friction).

As for equations, that's where I have a problem, I'm trying to have examples so I can then study those examples and solve new problems.
 
  • #4
BillTheButcher said:
No, there's no difference between the magnitude of the tension in problem 1.

As for the acceleration, in those problems, we are supposed to find:
normal force
tension
acceleration

Masses will be given, as well as coefficient of friction (only kinetic friction).

As for equations, that's where I have a problem, I'm trying to have examples so I can then study those examples and solve new problems.
I'll give you the first equation.

From free-body diagram, add the force vectors to find the net force:

[itex]\vec{F_M} = M\vec{g} + \vec{T} = M\vec{a_M}[/itex]

Since the net force is down, letting down be positive, the force magnitudes add this way:

[itex]F_M = Mg - T = Ma_M[/itex]

Can you write the similar equation for m? Then relate the two accelerations.

AM
 
  • #5


Hello,

Thank you for reaching out for help with your physics problems. Newton's Laws can be a challenging subject, but with some practice and understanding, you will be able to solve these problems with ease. Let's take a look at each of the problems and how to approach them using Newton's Laws.

1st Problem: In this problem, we have a block of mass 2kg on a frictionless surface, connected to a hanging mass of 3kg by a string that goes over a pulley. The question asks for the acceleration of the system and the tension in the string.

To solve this problem, we need to apply Newton's Second Law, which states that the net force on an object is equal to its mass times its acceleration (F=ma). In this case, we have two objects, the block and the hanging mass, and we need to consider the forces acting on each of them separately.

For the block, the only force acting on it is the tension in the string, which we will label as T. We can also label the acceleration of the block as a. So, using Newton's Second Law, we can write the equation: T=ma.

For the hanging mass, we have two forces acting on it: its weight (mg) and the tension in the string (T). Since the mass is hanging, we know that its acceleration is equal to the acceleration of the block (a). So, using Newton's Second Law, we can write the equation: mg-T=ma.

Now we have two equations and two unknowns (T and a). We can solve for both of them by setting the equations equal to each other and solving for a. This gives us a=mg/(m+M), where m is the mass of the hanging mass and M is the mass of the block. Plugging in the values, we get a=3kg*9.8m/s^2/(2kg+3kg)=4.9 m/s^2.

To find the tension in the string, we can plug this value of a back into our first equation (T=ma) and solve for T. This gives us T=2kg*4.9m/s^2=9.8N.

2nd Problem: In this problem, we have a block of mass 2kg on a frictionless surface, connected to a spring with a spring constant of 10 N/m. The question asks for the maximum
 

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1. How are Newton's Laws applied to systems?

Newton's Laws are applied to systems by considering the overall forces acting on the system and how they affect the motion of the system as a whole. This can involve breaking down the system into smaller parts and analyzing the forces acting on each individual part, as well as considering the effects of external forces on the entire system.

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3. How do Newton's Laws affect car crashes?

Newton's Laws play a crucial role in understanding car crashes. The first law explains how an object, such as a car, will continue moving in a straight line at a constant speed unless acted upon by an external force. In a car crash, the external force is the impact with another car or object. The second law describes how the force of the impact is directly proportional to the mass of the car and its acceleration, which can help determine the severity of the crash. And the third law explains how the two cars involved in the crash will experience equal and opposite forces, contributing to the overall impact.

4. How does Newton's Third Law apply to sports?

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