Physics, 31.12.2019 04:31 oneicyahdaley10

Awave pulse travels along a string at a speed of 160cm/s . note that parts a - d are independent and refer to changes made to the original string.

a)what will be the speed if the string's tension is doubled?

b)what will be the speed if the string's mass is quadrupled (but its length is unchanged)?

c)what will be the speed if the string's length is quadrupled (but its mass is unchanged)?

d)what will be the speed if the string's mass and length are both quadrupled?

Answers: 1

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Answer from: queenliz855

a) $v'=\sqrt{2} \times v$

Speed will become √(2) times the initial speed.

b) $v'=\frac{1}{2}\times v$

i.e Speed of the pulse becomes half of the initial speed.

c) $v'=2 \times v$

i.e Speed of the pulse becomes twice of the initial speed.

d) v'= v

i.e Speed of the pulse remains the same as initial.

Explanation:

Given:

speed of wave pulse along a string, $v=160\ cm.s^{-1}$

We know the relation between the velocity of wave pulse in a string, tension in the string and its linear mass density as:

$v=\sqrt{\frac{T}{\mu} }$ initially

where:

tension in the string

$\mu=\frac{m}{l}$ is the linear mass density as mass per unit length of the string.

Speed of the pulse if the tension is doubled:

$v'=\sqrt{\frac{2T}{\mu} }$

$v'=\sqrt{2} \times v$

Speed will become √(2) times the initial speed.

Speed of the pulse if the mass of the string is quadrupled:

We firstly find μ for this string.

$\mu'=\frac{4m}{l}$

i.e

$\mu'=4\mu$

Now,

$v'=\sqrt{\frac{T}{4\mu} }$

$v'=\frac{1}{2}\times v$

i.e Speed of the pulse becomes half of the initial speed.

Speed of the pulse if the length of the string is quadrupled:

We firstly find μ for this string.

$\mu'=\frac{m}{4l}$

i.e

$\mu'=\frac{ \mu}{4}$

Now,

$v'=\sqrt{\frac{T}{\frac{m}{4l} }$

$v'=2 \times v$

i.e Speed of the pulse becomes twice of the initial speed.

Speed of the pulse if both the length & the mass of the string is quadrupled:

We firstly find μ for this string.

$\mu'=\frac{4m}{4l}$

i.e

$\mu'=\mu$

Now,

$v'=\sqrt{\frac{T}{\mu} }$

v'= v

i.e Speed of the pulse remains the same as initial.

Answer from: Quest

i think its c if i'm wrong

Answer from: Quest

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol

b. a hockey puck sliding across the ice

c. a compressed spring

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice is the correct option.

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Awave pulse travels along a string at a speed of 160cm/s . note that parts a - d are independent and...

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