problem on force and acceleration

Topic :-Force and Acceleration

The velocity of a moving object is the rate at which its position or location changes and is measured in units of length per time,in other words,
when we apply some force on an object then the acceleration will increase accordingly.So the force and acceleration are directly proportional to each other.


Queston:-An electron in a television picture tube moves towards the front of the tube with a speed of 8.0x10^6m/s along the x axis surrounding the neck of the tube are coils of wire that create a magnetic field of magnitude 0.0025T, directed at an angle of 60degrees to the x axis and lying in the x y plane . Calculate the magnetic force on and acceleration of the electron (charge of electron -1.6x10^-19C and mass is 9.11x10^-31kg. find the net?

Answer:

Given
Net force=2.77*10^-15 N,
Acceleration=.304*10¹⁶m/sec^2


Here,
V=8.0x10⁶m/s
B=0.0025T(magnetic field's of magnitude)
Q=charge of electron -1.6x10^-19C
Mass = 9.11x10^-31kg

The formula to find force is
F=q (V*B)

=QVB sin θ
= QVB sin 60
=2.77*10^-15 N

So,
Net force=2.77*10^-15 N
Direction = Z direction

                              
                     F
      Acceleration=------
                     m

                  = .304*1016m/sec^2

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Question on Frequencies at different Resonance

Waves and Sounds is one of the basic concept in Physics which deals with wavelength, frequency and velocity of waves and sounds under uniform motion. Initial Frequency generated by any instrument is called as fundamental frequency and sound harmonics.

Topic : Vibrating String with a property of Resonance

Resonance is the tendency of an instrument to vibrate with large amplitude.

Question : A particular string resonates in four loops at a frequency of 280 Hz. Name at least three other frequencies at which it will resonate.

Solution :

Four loops means four anti-nodes, which means that we have the fourth harmonic, as the fundamental is one "loop" or anti-node.

The fourth harmonic would be four times the fundamental, so therefore the fundamental is 280 Hz/4 = 70 Hz,

and the next two would be 140 Hz, and 210 Hz.

So f₁ = 70Hz (fundamental frequency)
f₂ = 2f₁ = 2 x 70 = 140 Hz
f₃ = 3f₁ = 3 x 70 = 210 Hz
f₄ = 4f₁ = 4 x 70 = 280 Hz

For more explanations related to the concept can be found in physics help or science help.