Solve f=ma Problem: Find Acceleration, Forces on Blocks

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In summary, the three blocks of different masses are in contact with each other on a frictionless, horizontal surface. A horizontal force of 18n is applied to each block, causing them to accelerate. The net forces on each block are found to be (18n)(2kg)(3kg)(4kg), and the contact forces between the blocks are (18n)(2kg)(3kg)(4kg).
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Homework Statement



three blocks (m1=2kg, m2=3kg, m3= 4kg) are in contact with each other on a frictionless, horizontal surface as shown below. a horizontal force f=18n is applied to m1. blocks look like this --force-->(m1)(m2)(m3)

find the acceleration of the blocks

find the magnitudes of the net forces on each block

find the magnitudes of the contact forces between the blocks

Homework Equations



f=ma
f=mg



The Attempt at a Solution



for the acceleration of the blocks part, is it f=ma?
so for block one is it 18=2a
block 2 is it 18=3a
and block 3 18=4?

i don't know for the next 2 parts

thanks
 
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  • #2
Can you visualize this problem at all? Imagine an air hockey table with 3 blocks of different sizes ranging from smallest to largest. And you push against the smallest. What happens? Would the three blocks separate? Your eqns would suggest that this is the case. If it were so, maybe I could arrange ever increasing weights on a string, like a clothes line and knock on one, and the 50'th flies off at 2000mph. I like to add comments like these as I think trying to get your minds eye around these situations can be very helpful in focusing on a soln.

Now you have posted a couple of eqns, one of which is helpful, the other has no bearing because in this case friction has been preempted. So weight f=mg doesn't matter. You're missing a crucial eqn, any idea about which one? Hint: go back to the beginning of your text chapter and look at all three of Newtons laws.
 
  • #3
To solve the above you can either draw the free body diagrams of each body and then mess with it for a long tym, or simple consider the three bodies as one for the first part of the question.
Thus, the mass of the new combined block is 10 kg.
Now find the accln.
After this, you need to work out the contact forces, say N1 and N2 by writing out individual force equations for each block starting with the 2 kg block. Try it and tell me what your answers are...
 
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1. What is the formula for solving f=ma?

The formula for solving f=ma is f=ma, where f represents the net force, m represents the mass of the object, and a represents the acceleration.

2. How do I find the acceleration in this problem?

To find the acceleration, you can rearrange the formula f=ma to solve for a. This would give you a=f/m, where a is the acceleration, f is the net force, and m is the mass of the object.

3. What are the units for force, mass, and acceleration?

The units for force are typically measured in Newtons (N), mass is measured in kilograms (kg), and acceleration is measured in meters per second squared (m/s^2).

4. How do I determine the forces acting on the blocks in this problem?

To determine the forces acting on the blocks, you can use the formula f=ma and plug in the known values for mass and acceleration. These forces can include gravity, friction, or applied forces.

5. Can I use this formula for any type of problem involving forces and acceleration?

Yes, the formula f=ma can be used for any problem involving forces and acceleration, as long as the mass and acceleration values are known. However, it may be necessary to use additional formulas or equations depending on the specific problem.

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