Tuesday, June 23, 2009

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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Friday, June 5, 2009

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.


Monday, May 18, 2009

Question to Determine Velocity of Rollar Coaster

Roller coaster’s motion is a type of motion. Here is a word problem to determine the velocity of moving roller coaster. Balanced or unbalanced forces when applied on any body there occur a motion and the speed at which the body moves is velocity of that body.

Topic : Velocity of Moving Body

Since Potential Energy is equal to Kinetic energy in the system, m*g*h = 1/2*m*v2 is the formula to find velocity of a body with mass m, height h and g is constant gravitational force.

Question : A roller coaster is 94.5 m high at its highest point. What is the maximum possible speed of the roller coaster? The roller coaster’s actual maximum speed is 41.1 m/s.?

Solution :
Height=94.5 metre
Actual maximum speed is 41.1 m/s.
The roller coaster reaches maximum speed when all of its gravitational potential energy has been converted to kinetic energy


Here PE = KE
M*g*h=1/2*m*v2

V2=2*g*h=2*9.8*94.5= 1852.2

V= 43.037 m/sec

The maximum possible speed of the roller coaster, V= 43.037 m/sec


Whenever you have to solve similar kind of question, like finding velocity or any unknown qantities, consider the same formula substitute the values and calculate.

If you have any kind of queries related to the above motion topic please do write to our
physics help.