Solving for Velocity and Describing Motion of a Spring-Mass System

[riseofphoenix]

#7.

This is what i tried to do... but I got it wrong :( Please help

T ≈ 2π√(L/g)

1.31 = 2π√(L/9.81)
1.31/2π = √(L/9.81)
2.057 = √(L/9.81)
2.057² = L/9.81
4.2343 = L/9.81
4.2343(9.81) = L
41.54/1000 = L
0.0415 = L

"INCORRECT: Your response differs from the correct answer by more than 100%. "

 

[riseofphoenix]

Wow where is everybody?

 

[riseofphoenix]

Hello?

 

[SammyS]

#7.

This is what i tried to do... but I got it wrong :( Please help

T ≈ 2π√(L/g)

1.31 = 2π√(L/9.81)
1.31/2π = √(L/9.81)
2.057 = √(L/9.81)
2.057² = L/9.81
4.2343 = L/9.81
4.2343(9.81) = L
41.54/1000 = L
0.0415 = L

"INCORRECT: Your response differs from the correct answer by more than 100%. "

One clue is the mention of the moment of inertia.

Another is that it's a physical pendulum.

Also,

Don't bump your thread until it's been here for 24 hours.​

 

[riseofphoenix]

One clue is the mention of the moment of inertia.

Another is that it's a physical pendulum.

Also,

Don't bump your thread until it's been here for 24 hours.​

I =T²MgD/4π²
I = [(1.31²)(0.246)(9.81)(18)]/39.478
I = 74.545/39.478
I = 1.8882

"INCORRECT"

-___-
AKFJDJFDAKLNDJK

 

[SammyS]

I =T²MgD/4π²
I = [(1.31²)(0.246)(9.81)(18)]/39.478
I = 74.545/39.478
I = 1.8882

"INCORRECT"

-___-
AKFJDJFDAKLNDJK

Convert centimeters to meters.

 

[riseofphoenix]

Convert centimeters to meters.

Oh...

0.0188

"CORRECT"

-.- The day I graduate from Webassign...

Thank you...

What about this last one? I have no idea where to start/what equation to use.

#3. A 40.0-g object is attached to a horizontal spring with a force constant of 10.0 N/m and released from rest with an amplitude of 20.0 cm. What is the velocity of the object when it is halfway to the equilibrium position if the surface is frictionless?
m/s

 

[SammyS]

Oh...

0.0188

"CORRECT"

-.- The day I graduate from Webassign...

Thank you...

What about this last one? I have no idea where to start/what equation to use.

#3. A 40.0-g object is attached to a horizontal spring with a force constant of 10.0 N/m and released from rest with an amplitude of 20.0 cm. What is the velocity of the object when it is halfway to the equilibrium position if the surface is frictionless?
m/s

Describe the motion of the object after being released.