Physics test in an hour. Can someone explain how to do this for me?

Question

A spring-block is pictured below. The equilibrium position of the spring is at the position of x= 0 and the spring is compressed and is at position x= -4.0 cm. The spring constant of the spring is k=125.0 N/m. Using Hooke's Law, conservation of energy and ignoring friction:
1) What is the elastic potential energy stored in the spring as it is pictured below?

2) If the velocity of the block is 2.0 m/s at position x=0 (assume all the potential energy has been converted to kinetic energy), what is the mass of the block?

Please help me understand this. I'm trying to study for my physics test and do not understand how to do this problem. Equations would be helpful and if you could work it out that would be even more helpful but I would settle for equations and where to plug in the numbers

Answer 1

elastic potential energy stored is 1/2 k x^2 where x is displacement from equilibrium position



when fully compressed, the spring has PE of 1/2 kx^2



at x=0, all the PE is converted to KE so we equate



1/2 kx^2 = 1/2 mv^2 where x is the distance of max compression, 0.04m



solving for v:



v= x Sqrt[k/m]



2m/s = 0.04m Sqrt[125N/m / m]



square both sides:



4 (m/s)^2 = 1.6x10^-3 m^2 (125N/m / mass)



mass = 1.6x10^-3*125/4 kg = 0.05kg

Answer 2

PE elastic = 1/2 k x^2 = 1/2 (125.0) (0.040^2) = 0.10 J (remember to use MKS units)



at x = 0 the KE of the block will equal the PE of the spring at -4 cm

KE = 1/2 m v^2

0.10 = 1/2 m (2.0^2)

m = 0.050 kg or 50 g

Answer 3

potential energy in a spring from Hooke's Law is P.E. = 1/2kx^2

k is the spring constant. It is in N/m The more force it takes to stretch the spring a certain distance, the higher the k constant. So stiffer springs have a bigger k constant.



Obviously I did not need to go about explaining the law of conservation of energy because he did it above and to restate his answer would not help. But I hope I gave a better idea of the concept of the k constant in a spring.

Answer 4

You sound desperate and arranged to artwork and seem doing the proper form of issues. you have pointed out time administration as a difficulty your self, i anticipate which you will %. off the questions you be attentive to you're able to do first and attempt to stick to time /question in accordance to marks. Do you get the artwork lower back so which you will discover the place you're lacking the marks (i'm hoping so, yet i be attentive to that is not consistently the case). sometimes misreading/fake impression questions reduces your mark. are you able to be certain with (or with out the artwork) what areas are inflicting issues? you are able to desire to be doing somewhat stuff properly, it may be extra useful to pay interest on weaker areas. there are a lot of questions in Yahoo that are given precise and special solutions - seeing the thank you to word the formulae would help you. follow it, Physics is a great problem and covers numerous distinctive fields of learn!