Velocity, because if an object is in motion with no direction we will consider it as speed, but if it has direction we will consider it as Velocity. Hope it helps
Answer:
Explanation:
The energy of a photon is given by the equation
, where h is the <em>Planck constant</em> and f the frequency of the photon. Thus, N photons of frequency f will give an energy of
.
We also know that frequency and wavelength are related by
, so we have
, where c is the <em>speed of light</em>.
We will want the number of photons, so we can write

We need to know then how much energy do we have to calculate N. The equation of power is
, so for the power we have and considering 1 second we can calculate the total energy, and then only consider the 4% of it which will produce light, or better said, the N photons, which means it will be
.
Putting this paragraph in equations:
.
And then we can substitute everything in our equation for number of photons, in S.I. and getting the values of constants from tables:

Answer:
B) Degrees
Explanation:
The directions of the vectors are often defined in terms of due East, due North, due West and due South. A direction exactly in between of North and East can be described as Northeast, similarly we can describe directions in terms of Northwest, Southeast and South west.
From these, the direction of a vector can be easily expressed in degrees, which is measured counter clockwise about its tail from due East. Considering that we can say that East is at 0° , North is at 90° , West is at 180 and South is at 270° counter clockwise rotation from due East.
So, we know that the direction of a vector lying somewhere between due East i.e 0° and due North i.e 90°, will be measured in degrees, which will have a value between 0°-90°
Answer:
option (c) is correct
Explanation:
Half life of a substance is the time in which the element becomes half of is initial value.
half life, T = 8 days
Amount remaining, N = 10 % of original value
Let the original value is No.
N = 10% of No
N = 0.1 No
Let the time taken is t and the decay constant is λ.
The relation between the decay constant and the half life is given by

Us the equation of radioactivity



Taking natural log on both the sides, we get
0.08664 t = 2.303
t = 26.6 days