Answer:
option A
Explanation:
given,
Force = F
angle = θ
weight on suitcase = mg
distance = d
constant velocity so, acceleration a = 0
coefficient of friction = µ
Work done = ?
Work done is equal to force into displacement.
Friction act opposite to the force acting so, work done by frictional force will be negative.
frictional force will act into horizontal direction opposite to force.
here displacement is equal to d
now,
W = -F d cos θ
Hence,the correct answer is option A
An opera singer breaks a thin glass with only the use of her high frequency voice
Answer:
actually I was just wondering what you are thinking
Answer:
1.
and
2.
Explanation:
The energy of a photon is given by the so-called Planck-Einstein relation:

where E is the energy, f the frequency,
the wavelength, c the speed of light and h the planck constant
So, we have:

And:

2. The work function is the amount of energy required to remove an electron from the material. Therefore the kinetic energy of the photoelectrons will be the energy of the electromagnetic radiation minus the work function:

Where K is the kinetic energy and W the work function, for copper W=4.7eV
Rewriting for
:

This wavelength corresponds to the ultraviolet range