Confirm my answers on Oscillating Springs?

[vtmvick7]

confirm my answers on Oscillating Springs??

Can anyone confirm or adjust my answers for problems 12 and 14? Also can someone help me start on problem 13.. Thanks guys I really appreciate the help

Homework Statement

012
Find the speed of the block when it is 2.5 cm
from the equilibrium position.
Answer in units of m/s.

013
Find its acceleration at 2.5 cm from the equilibrium position.
Answer in units of m/s2.

014
Find the time it takes the block to move from
x = 0 to x = 2.5 cm.
Answer in units of s.

Homework Equations

M= 0.7kg
k= 14.7 N/m
A= 5cm
w= 4.58 rads/s
T= 1.37s

The Attempt at a Solution

#14: x(t) = 5cm Cos(4.58rads/s*(t))
t= (1/4.58 rads/s) cos^-1 (2.5cm/5cm) = 13.09s??
do I convert it to meters??

#12: E=1/2mv^2 + 1/2kx^2 = 1/2ka^2
1/2(.7)v^2 + 1/2(14.7)(.025m)^2 = 1/2(14.7)(.05m)^2
.35v^2=.0137
v=0.1984m/s
I changed the cm to m, I should have done this right??

 

[vtmvick7]

I think I solved #13.. would I use the equation

a = -w^2 * x?

 

[Bearbull24.5]

I think that works but that is the equation for maximum acceleration. This means that equation might not always work for a problem such as this. Is acceleration always at maximum when it is half the distance from the equilibrium? (I don't know the answer to this)

I did this problem a different way.

https://www.physicsforums.com/showthread.php?t=397323