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o-na [289]
3 years ago
7

In old times, before there were train signals, people who worked on the railroad would often put their ear down to the train tra

ck to listen for an oncoming train. Why would this result in hearing the train further off than just listening for the train through the air? Question 3 options: Sound travels slower in air because there are often trees and other items blocking the sound. People did not do this because sound travels faster through less dense material, like air, rather than more dense materiel, like train tracks. Sound travels slower, but louder through solid material because it is more dense, so the train could be heard better this way. Sound waves travel faster in more dense material, and the more dense the material the faster the sound is.
Physics
1 answer:
elena55 [62]3 years ago
8 0
The answer is the second option or B.
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In the figure, a weightlifter's barbell consists of two identical small but dense spherical weights, each of mass 50 kg. These w
kondaur [170]

The moment of inertia is 24.8 kg m^2

Explanation:

The total moment of inertia of the system is the sum of the moment of inertia of the rod + the moment of inertia of the two balls.

The moment of inertia of the rod about its centre is given by

I_r = \frac{1}{12}ML^2

where

M = 24 kg is the mass of the rod

L = 0.96 m is the length of the rod

Substituting,

I_r = \frac{1}{12}(24)(0.96)^2=1.84 kg m^2

The moment of inertia of one ball is given by

I_b = mr^2

where

m = 50 kg is the mass of the ball

r=\frac{L}{2}=\frac{0.96}{2}=0.48 m is the distance of each ball from the axis of rotation

So we have

I_b = (50)(0.48)^2=11.5 kg m^2

Therefore, the total moment of inertia of the system is

I=I_r + 2I_b = 1.84+ 2(11.5)=24.8 kg m^2

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6 0
3 years ago
A block is pulled across a flat surface at a constant speed using a force of 50 newtons at an angle of 60 degrees above the hori
vladimir2022 [97]

The magnitude of the friction force is 25 N

Explanation:

To solve this problem, we just have to analyze the forces acting on the block along the horizontal direction. We have:

  • The horizontal component of the pulling force, F cos \theta, where F = 50 N is the magnitude and \theta=60^{\circ} is the angle between the direction of the force and the horizontal; this force acts in the  forward direction
  • The force of friction, F_f, acting in the backward direction

According to Newton's second law, the net force acting on the block in the horizontal direction must be equal to the product between the mass of the block and its acceleration:

\sum F_x = ma_x

where

m is the mass of the block

a_x is the horizontal acceleration

However, the block is moving at constant speed, so the acceleration is zero:

a_x = 0

So the equation becomes

\sum F_x = 0 (1)

The net force here is given by

\sum F_x = F cos \theta - F_f (2)

And so, by combining (1) and (2), we find the magnitude of the friction force:

F cos \theta - F_f = 0\\F_f = F cos \theta = (50)(cos 60^{\circ})=25 N

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4 0
2 years ago
You push a bike pedal 10cm and the bike moves 100cm. Calculate the Speed ratio ( show all work ) ( use the formula and divide th
scZoUnD [109]

Answer:

when you are pushing the pedal you are causing the pedal to move done and then you will move 100cm

Explanation:

10 cm= 100 cm moved so when you move you will move because you are timeing  the 10 by 100 to get the spped

3 0
2 years ago
The law of reflection says that the angle of incidence is
nekit [7.7K]
The law of reflection states that the angle of incidence is equal to the angle of reflection. Furthermore, the law of reflection states that the incident ray, the reflected ray and the normal all lie in the same plane.

hope this helps :)

4 0
3 years ago
One type of potential energy is gravitational potential energy. What is necessary for an object to have gravitational potential
galben [10]

Answer:

Gravitational potential energy is energy an object possesses because of its position in a gravitational field. Since the force required to lift it is equal to its weight, it follows that the gravitational potential energy is equal to its weight times the height to which it is lifted.

5 0
2 years ago
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