Calculating Distance Using Spring Constants: 20-Minute Crash Course

[grbmrdj]

Calculating distance using spring constant, mass and velocity? (Really basic stuff!)

Hi I have a physics exam tomorrow, and I just realized we haven't covered either impulse or spring constants, and about 1 1/2 hours left to study. From a practice exam, please someone help me out?

Homework Statement

A high impact crash helmet is glued onto a floor and a 5.0kg steel ball is dropped from a certain height in the helmet padding. The ball hits the helmet padding at 0.85m/s. The spring constant of the padding amterial is 35kN/m.

Homework Equations

distance = Force/spring constant(k)
Most likely an impulse on as well

The Attempt at a Solution

d=F/k
impulse = mv = 5 x 0.85 = 4.25
d = 4.25 / 35000 = 1.2 x 10^-4

This one is not so important:
Also, in a previous question, they gave a linear graph, at one point, N = 300 and displacement = 0.06 metres. Find the spring constant?

I got
k = f/d = 300/0.06 = 5000 N/m

Is this right? (Couldn't find the answer's to the practice exam)

Also, any tips on learning these in about 20 minutes? Thanks, and sorry for massive post.

 

[jbsteele]

Yes, your answer for the second question is correct. As for learning in 20 minutes, here are some tips: -Make sure you understand the basic concepts of spring constant, force, and impulse. -Try to work through some practice problems to build your confidence. -Review some examples of how force, impulse and spring constant interact with each other. -Focus on understanding the equations and how to apply them to solve problems. -Think about how the different variables (mass, velocity, etc.) relate to each other. -If you still have time, take a few practice tests to get used to the types of questions you might get on your exam.