Energy of a wave:
E = nhc/λ
3000 = (n x 6.63 x 10⁻³⁴ x 3 x 10⁸)/(510 x 10⁻⁹)
n = 7.69 x 10 ²¹ photons per second per meter²
2.70 cm² = 2.70/10,000 m²
= 2.7 x 10⁻⁴
Photons per second = 7.69 x 10 ²¹ x 2.7 x 10⁻⁴
= 2.08 x 10¹⁸ photons per second
Answer:
So the conclusion is that in presence of air net force acting downward reduces for feather and hence falls slower than coin. But in absence of air resistance, net downward force is just equal to force due to gravity which is same for both coin and feather and hence they fall down at the same rate.
Answer:
time required after impact for a puck is 2.18 seconds
Explanation:
given data
mass = 30 g = 0.03 kg
diameter = 100 mm = 0.1 m
thick = 0.1 mm = 1 ×
m
dynamic viscosity = 1.75 ×
Ns/m²
air temperature = 15°C
to find out
time required after impact for a puck to lose 10%
solution
we know velocity varies here 0 to v
we consider here initial velocity = v
so final velocity = 0.9v
so change in velocity is du = v
and clearance dy = h
and shear stress acting on surface is here express as
= µ 
so
= µ 
............1
put here value
= 1.75× × 
= 0.175 v
and
area between air and puck is given by
Area = 
area = 
area = 7.85 × 
m²
so
force on puck is express as
Force = × area
force = 0.175 v × 7.85 × 
force = 1.374 × v
and now apply newton second law
force = mass × acceleration
- force = 
- 1.374 × v = 
t = 
time = 2.18
so time required after impact for a puck is 2.18 seconds
<span>The correct answer is blue. If you look at a luminosity star chart, called the Hertzsprung Russell Diagram, you will see the measurement of luminosity on the left side, and you will see a curve of stars with different colors (which correlate to the colors of the stars). Look for 30 on the luminosity measurement (look between 1 and 100). Then, move horizontally across the diagram until you hit the stars, whose color will be blue. Thus, blue is the answer.</span>
Answer:
v = 12.86 km/h
v = 3.6 m/s
Explanation:
Given,
The distance, d = 13.5 km
The time, t = 21/20 h
= 1.05 h
The velocity of a body is defined as the distance traveled by the time taken.
v = d / t
= 13.5 km / 1.05 h
= 12.86 km/h
The conversion of km/h to m/s
1 km/h = 0.28 m/s
12.86 km/h = 12.86 x 0.28 m/s
= 3.6 m/s
Hence, the velocity in m/s is, v = 3.6 m/s
