Answer:
For a material to be a good conductor, the electricity passed through it must be able to move the electrons; the more free electrons in a metal, the greater its conductivity.
Answer:
a) 4.9W b) 3.82W
Explanation:
Stefan-Boltzmann law of radiation formulae:
Q/t (W) = sigma* e*A*T^4
Sigma = 5.67*10^-8 j/sm^2K^4 (Stefano Boltzmann constant)
e = emissivity
T = absolute temperature in kelvin and A = area in m^2
a) Q/t = 140/10000(m^2) * 0.87* 5.67* 10^-8* (290^4) = 4.9W
b) without hair the
Q/t = 140/ 10000(m^2) *0.68* 5.67* 10^-8* (290^4)
= 3.82W
We use the kinematic equations,
(A)
(B)
Here, u is initial velocity, v is final velocity, a is acceleration and t is time.
Given, 
, 
and 
.
Substituting these values in equation (B), we get
.
Therefore from equation (A),
Thus, the magnitude of the boat's final velocity is 10.84 m/s and the time taken by boat to travel the distance 280 m is 51.63 s
Answer:
People with presbyopia require a convex lens for reading glasses; specialized preparations of convex lenses usually require the services of an optometrist
