Ask Experts Questions for FREE Help !
Ask
    Shira S's Avatar
    Shira S Posts: 5, Reputation: 1
    New Member
    		  
    #1

    Dec 16, 2016, 05:51 AM
    Elastic Energy - finding mass
    A block is pushing a spring with spring constant k=80N/m. The spring is compressed by 10cm. The block is released and stops 40 cm away from the point of compression.


    What is the mass of the block if the kinetic friction coefficient between the block and the ground is .15?
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
    		  
    #2

    Dec 16, 2016, 07:58 AM
    As with your other post - please show us your attempt at solving this and we'll help if you get stuck. But here's a hint to get you started: equate the PE of the compressed spring with the work done by friction on the block (force of friction times distance traveled).
    Shira S's Avatar
    Shira S Posts: 5, Reputation: 1
    New Member
    		  
    #3

    Dec 19, 2016, 10:49 AM
    Thank you!
    Using your method I got the answer:)

    I still don't understand though - why we can equate work of friction to the potential energy of the spring?
    ebaines's Avatar
    ebaines Posts: 12,131, Reputation: 1307
    Expert
    		  
    #4

    Dec 19, 2016, 12:37 PM
    There is a principle that the energy expended to do work is equal to the work itself. When the spring is compressed the object is at rest, so its energy is equal to the PE of the compressed spring. When the spring is released all the PE is converted into kinetic energy (KE). Then as the object slides along the surface it loses KE due to having to oppose the force of friction, and the amount of work it does is equal to the force of friction times the distance it distance it sides. When the block comes to rest it has no KE left. Hence the amount of work performed by the block equals the KE it had after being releases by the spring, which equals the PE that the spring started with.
Not your question? Ask your question View similar questions
 

Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.


Check out some similar questions!

What is the kinetic energy of a disk with a mass of 0.2 g when thrown with a speed of [ 0 Answers ]

What is the kinetic energy of a disk with a mass of 0.2 g when thrown with a speed of 15.8 km/hr?

Deriving the equation for the rest-mass energy of a non relativistic object [ 0 Answers ]

Hello I am asked to derive this formula by applying a binomial expansion to the expression for 'gamma factor' (that funny y shaped symbol). To make things clear I will denote gamma as 'y' and beta as 'b' Now I know that yb = ((y-1)(y+1))^1/2 and have proved it by changing b into an expression...

Converting mass into energy? [ 1 Answers ]

calculate how much energy would be released if each of the following masses were converted into entirely into their equivalent energy: (A) a carbon atom of with a mass of 2 X 10^-26. (B) 1 kilogram. (C) a planet as massive as the Earth (6 X 10^24).

Transferrence of energy to mass [ 1 Answers ]

I am trying to teach myself physics this summer and have just come across Eistein's e=mc2 formula. This gives a correlation between energy and mass, and that when energy is imparted to an object the object will gain mass, and in the presence of gravity weight. Does this mean that energy has an...

Work + Elastic Potential Energy [ 2 Answers ]

A 50g ice cube can slide w/o friction up and down a 30 degree slope. The ice cube is pressed against a spring at the bottom of the slope, compressing the spring 10 cm. The spring constant is 25N/m. When the ice is released, what total d will ti travel up the slope before reversing direction? W =...

View more questions Search