Answer:
the number density of the protons in the beam is 3.2 × 10¹³ m⁻³
Explanation:
Given that;
diameter D = 2.0 mm
current I = 1.0 mA
K.E of each proton is 20 MeV
the number density of the protons in the beam = ?
Now, we make use of the relation between current and drift velocity
I = MeAv ⇒ 1 / eAv
The kinetic energy of protons is given by;
K = 
v²
v = √( 2K /
)
lets relate the cross-sectional area A of the beam to its diameter D;
A =
πD²
now, we substitute for v and A
n = I /
πeD² ×√( 2K /
)
n = 4I/π eD² × √(
/ 2K )
so we plug in our values;
n = ((4×1.0 mA)/(π(1.602×10⁻¹⁹C)(2mm)²) × √(1.673×10⁻²⁷kg / 2×( 20 MeV)(1.602×10⁻¹⁹ J/ev )
n = 1.98695 × 10¹⁸ × 1.6157967 × 10⁻⁵
n = 3.2 × 10¹³ m⁻³
Therefore, the number density of the protons in the beam is 3.2 × 10¹³ m⁻³
Answer:
<h2>
<u>Joule</u><u>:</u></h2>
1 Joule of work is said to be done when a force of 1 Newton is applied to move/displace a body by 1 metre.
1 Joule= 1 Newton × 1 metre
1 Newton is the amount of force required to accelerate body of mass 1 kg by 1m/s²
So units of N is kgm/s²
So,
1 Joule
=1kgm/s² × m
=1kgm²/s²
<h2><u>Erg</u><u>:</u></h2>
1 erg is the amount of work done by a force of 1 dyne exerted for a distance of one centimetre.
1 Erg =1 Dyne × 1 cm
1 dyne is the force required to cause a mass of 1 gram to accelerate at a rate of 1cm/s².
1 Erg=1 gmcm/s² × cm
1 Erg=1 gmcm/s² × cm=1gmcm²/s²
this is what you need to convert 1gmcm²/s² to 1kgm²/s²
<h3><u>
what you need to know for conversion</u></h3>
[1gm=0.001kg
1cm²
=1cm ×1cm
=0.01 m × 0.01 m
=0.0001m²
second remains constant
]
So,
1gmcm²/s²
=0.001kg×0.0001m²/s²
=0.001kg×0.0001m²/s² =0.0000001kgm²/s²
Hence,
<h3>
<u>1 Erg</u><u>=</u><u>0.0000001</u><u> </u><u>Joule</u></h3><h3>
<u>1</u><u> </u><u>Joule</u><u>=</u><u>1</u><u>0</u><u>,</u><u>0</u><u>0</u><u>0</u><u>,</u><u>0</u><u>0</u><u>0</u><u> </u><u>Erg</u></h3>
<h2>⇒15 J=15×10000000 Erg</h2><h2> =150000000 Erg</h2><h2>
=1.5×10⁶ Erg</h2>
Answer:
friction reduces the efficiency of machines, thus we must reduce the friction force that is acting upon it.