Find mass m when frequency changes from 0.88 Hz to 0.60 Hz after adding 600 g

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pupatel
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Need help please...I am having trouble with this question... :confused:

A mass m at the end of a spring vibrates with a frequency of 0.88 Hz. When an additional 600 g mass is added to m, the frequency is 0.60 Hz. What is the value of m?
 
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A 25.0 g bullet strikes a 0.600 kg block attached to a fixed horizontal spring whose spring constant is 6.70 * 10^3 N/m and sets it into vibration with an amplitude of 21.5 cm. What was the speed of the bullet before impact if the two objects move together after impact? :eek:
 
This seems very easy, but no matter what I do it doesn't give me the right answer...how do I do this? :frown:

A cord of mass 0.50 kg is stretched between two supports 27 m apart. If the tension in the cord is 145 N, how long will it take a pulse to travel from one support to the other?
 
You have the tension and the mass per unit length. There is a formula in your textbook that will provide the speed of the wave given those values.

How do you know the right answer is THE right answer?
 
alright. the speed of a wave in a string is equal to the root of the tension over the linear mass density. so v=(145N/(0.5kg/27m))^1/2. this gives you an anwser for velocity that is about 88.5 m/s so the time required for a pulse to travel the distance between the two supports is 27m/88.5m/s=0.305s.
 
the frequency is proportional to one over the root of the mass. I think you should be able to figure it out from here.
 
try conservation of energy...

also, I believe there is a separate section for homework help...
 
Not only is there a homework section but you will find that it is much easier for others to respond if either you create a single thread for all questions or title each thread differently. Multiple threads with the same title create nothing but confusion.
 
pupatel said:
Need help please...I am having trouble with this question... :confused:

A mass m at the end of a spring vibrates with a frequency of 0.88 Hz. When an additional 600 g mass is added to m, the frequency is 0.60 Hz. What is the value of m?

What is the relation between frequency and
Spring constant and mass

Note that you have been given 2 unknowns, spring constant k and original mass m.

The two expressions for the frequency give you two equations in these two unknowns.