Answer:
3.82 ms
Explanation:
The period of a wave is equal to the reciprocal of the frequency:

where f is the frequency.
In this problem, f = 262 Hz, so the period if this sound wave is

A) 
The energy of an x-ray photon used for single dental x-rays is

The energy of a photon is related to its wavelength by the equation

where
is the Planck constant
is the speed of light
is the wavelength
Re-arranging the equation for the wavelength, we find

B) 
The energy of an x-ray photon used in microtomography is 2.5 times greater than the energy of the photon used in part A), so its energy is

And so, by using the same formula we used in part A), we can calculate the corresponding wavelength:

Answer:
Change of momentum = M (Vf - (-Vi)) where V represents the scalar speeds of the ball or
I = M (ui + uf) and I is the impulse ΔM V = I Force = Change in Momentum
Answer:
The number of revolutions is 44.6.
Explanation:
We can find the revolutions of the wheel with the following equation:

Where:
: is the initial angular velocity = 13 rad/s
t: is the time = 8 s
α: is the angular acceleration
We can find the angular acceleration with the initial and final angular velocities:

Where:
: is the final angular velocity = 57 rad/s

Hence, the number of revolutions is:

Therefore, the number of revolutions is 44.6.
I hope it helps you!