Answer:
171.5 N
Explanation:
The gravitational force on an object due to the Earth is given by
where
m is the mass of the object
g is the acceleration due to gravity
The acceleration due to gravity at a certain height h above the Earth is given by
where:
G is the gravitational constant
is the Earth's mass
is the Earth's radius
Here,
So the acceleration due to gravity is
We know that the mass of the object is
m = 70 kg
So, the gravitational force on it is
Let's use Newton's 2nd law of motion:
Force = (mass) x (acceleration)
Force = (68 kg) x (1.2 m/s²) = 81.6 newtons .
Find the force that would be required in the absence of friction first, then calculate the force of friction and add them together. This is done because the friction force is going to have to be compensated for. We will need that much more force than we otherwise would to achieve the desired acceleration:
The friction force will be given by the normal force times the coefficient of friction. Here the normal force is just its weight, mg
Now the total force required is:
0.0702N+0.803N=0.873N
1) Frequency: 
the energy of the photon absorbed must be equal to the ionization enegy of the atom, which is
The energy of a photon is given by
where 
is the Planck's constant. By using the energy written above and by re-arranging thsi formula, we can calculate the frequency of the photon:
2) Wavelength: 91.2 nm
The wavelength of the photon can be found from its frequency, by using the following relationship:
where 
is the speed of light and f is the frequency. Substituting the frequency, we find
All of the above, work is a measurement of energy transfer, in Joules.
Potential energy = Joules
Kinetic energy = Joules
The key thing here is that anything having to do with just energy or energy transfer is measured in joules.
