# College Physics

posted by .

A 7 kg mass hangs on a 10 meter long weightless cord. To the nearest cm, what should the new length of the pendulum be in order that the new frequency be 1.8 times its current value?

The correct answer is 309 but I got 250.

Heres what I did..

(1/2pi)(sqrt g/L2) = (2/2pi)(sqrt g/L1)

1/L2 = 4/L1
4L2 = L1
L2 = L1/4

So 10/4 times 100cm/1m = 225...

• College Physics -

Sorry, I meant 250 not 225. Either way its still not the correct answer..

• College Physics -

ω₁= √(g/L₁)
ω₂=√(g/L₂)
1.8 ω₁=ω₂
1.8√(g/L₁)=√(g/L₂)
1.8²g/L₁=g/L₂
L₂=L₁/3.24=10/3.24 =
=3.086 ≈3.19 m = 309 cm

## Similar Questions

1. ### physics

A block of mass M hangs from a rubber cord. The block is supported so that the cord is not stretched. The unstretched length of the cord is L0 and its mass is m, much less than M. The "spring constant" for the cord is k. The block …
2. ### Physics

A block of mass M hangs from a rubber cord. The block is supported so that the cord is not stretched. The unstretched length of the cord is L_0 and its mass is m, much less than M. The "spring constant" for the cord is k. The block …
3. ### Physics

An elastic cord vibrates with a frequency of 2.7 Hz when a mass of 0.56 kg is hung from it. What will its frequency be if only 0.43 kg hangs from it?
4. ### Physics-Mechanics

horizontal surface. The block is connected by a cord passing over a pulley to another block of mass 5.53 kg which hangs in the air, as shown on the following picture. Assume the cord to be light (massless and weightless) and unstretchable …
5. ### College Physics

A child plays on a bungee cord and oscillates with a certain frequency f. An adult with a mass that is 16 times greater than that of the child then uses the same bungee cord. What is the ratio of the frequency with the adult to the …
6. ### physics

5. A 2.00-kg block hangs from a rubber cord, being supported so that the cord is not stretched. The unstretched length of the cord is 0.500 m, and its mass is 5.00 g. The “spring constant” for the cord is 100 N/m. The block is …
7. ### Physics

Two different simple harmonic oscillators have the same natural frequency (f=5.60 Hz) when they are on the surface of the Earth. The first oscillator is a pendulum, the second is a vertical spring and mass. If both systems are moved …
8. ### physics

A block of mass 4.44 kg lies on a frictionless horizontal surface. The block is connected by a cord passing over a pulley to another block of mass 6.55kg which hangs in the air , as shown above. Assume the cord to be light (massless …
9. ### physics

An elastic cord vibrates with a frequency of 3.5Hz when a mass of 0.62kg is hung from it.What is its frequency if only 0.40kg hangs from it?
10. ### Physics

Hi, I'm stuck with the following question: The acceleration due to gravity on Mars is only 3.75m/s^2. You would like to modify an antique grandfather clock so that it would still keep accurate time on Mars. If the length of the pendulum …

More Similar Questions