Position of Block when Spring Stops

In summary, the problem involves a block on a horizontal frictionless surface attached to a spring with a spring constant of 35 N/m. An applied force of 2.8 N pulls the block in the positive direction, stretching the spring until the block stops. The position of the block is found to be -0.08 m when the applied force and spring force are equal. However, the correct answer is 0.08 m and the work done by the applied force is negative. The rest of the problem follows standard principles.
  • #1
mochabcha
4
0
position of a spring!

Okay, Here's the problem
The block in Figure 7-11a (Figure not important) lies on a horizontal frictionless surface and is attached to the free end of the spring, with a spring constant of 35 N/m. Initially, the spring is at its relaxed length and the block is stationary at position x = 0. Then an applied force with a constant magnitude of 2.8 N pulls the block in the positive direction of the x axis, stretching the spring until the block stops. Assume that the stopping point is reached. (a) What is the position of the block? (b) What is the work that has been done on the block by the applied force? (c) What is the work that has been done on the block by the spring force?

(a) I drew a free body diagram and it seems like when the block stops the spring force catches up to the applied force counteracting it and stopping the motion of the block. So, Hooke's law states that F(spring) = -kx; since F(spring) = F(applied) --> F(applied) = -kx.
I crunched those numbers and got -.08 which made sense because the applied force is going to be positive [f(s) is negative in Hooke's law and x being a negative number will cancel the negatives].
BUT THAT'S WRONG what's the problem!
 
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  • #2
Does the block stop WHILE the force is still acting? If this is so then there is a point at which the net force on the block is zero. That means the friction (which will be opposite to instantaneous velocity), the spring force and the applied force will give rise to a net zero force at what you call the "stopping point". Rest of the problem seems pretty standard to me.
 
  • #3
The force is negative, so it's -2.8N and you should get 0.08 m. Then you can find the work which is negative too.
 

What is the "Position of Block when Spring Stops" experiment?

The "Position of Block when Spring Stops" experiment is a physics experiment that involves a block attached to a spring, which is then released from a certain height. The aim of the experiment is to determine the final position of the block when the spring fully stops moving.

What materials are needed for this experiment?

The materials needed for this experiment include a block with a known mass, a spring, a ruler or measuring tape, a stopwatch, and a support to hold the spring in place.

What factors can affect the final position of the block?

The final position of the block can be affected by various factors, such as the mass of the block, the spring constant, the initial height from which the block is released, air resistance, and any external forces acting on the block during its motion.

How do you perform the "Position of Block when Spring Stops" experiment?

To perform this experiment, first measure the mass of the block and note down the spring constant. Then, attach the block to the spring and release it from a certain height. Use the stopwatch to measure the time it takes for the spring to fully stop moving. Finally, use the ruler or measuring tape to determine the final position of the block.

What is the formula for calculating the final position of the block?

The formula for calculating the final position of the block is: x = mgh / k, where x is the final position of the block, m is the mass of the block, g is the acceleration due to gravity, h is the initial height of the block, and k is the spring constant.

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