Answer:
The answer to your question is: 13.2 m/s
Explanation:
final speed (fs) = 77 m/s
t = 6.5 s
gravity (g) = 9.81 m/s2
initial speed (is) = ?
Formula 
fs = is + gt     from this equation we clear "is" = fs - gt
Substitution                         is = 77 - (9,81)(6.5)
Process                               is = 77 - 63.8
                                             is = 13.2 m/s
 
        
             
        
        
        
Answer:
(B) The wavelength that a star radiates the most energy is inversely proportional to the temperature.
Explanation:
As we know that 
According to Wien's law wavelength is inverse proportional to the temperature .
   λ.T = Constant.
 λ.∝ 1 /T
As we know that star radiates wavelength and this wavelength is inverse proportional to the temperature of the star.
The temperature of cool star is cooler than the temperature of hot star that is cool star looks red and hot star looks blue.Cool star have low energy and hot star have high energy.
So option B is correct.
 (B) The wavelength that a star radiates the most energy is inversely proportional to the temperature.
 
        
             
        
        
        
It’s C because just trust
        
             
        
        
        
Answer:
The frequency is 302.05 Hz.
Explanation:
Given that,
Speed = 18.0 m/s
Suppose a train is traveling at 30.0 m/s relative to the ground in still air. The frequency of the note emitted by the train whistle is 262 Hz .
We need to calculate the frequency 
Using formula of frequency

Where, f = frequency 
v = speed of sound
 = speed of passenger
 = speed of passenger
 = speed of source
 = speed of source
Put the value into the formula


Hence, The frequency is 302.05 Hz.
 
        
             
        
        
        
The central force acting on the electron as it revolves in a circular orbit is  .
.
The given parameters;
- <em>speed of electron, v = 2.2 x 10⁶ m/s</em>
- <em>radius of the circle, r = 4.63 x 10⁻¹¹ m</em>
<em />
The central force acting on the electron as it revolves in a circular orbit is calculated as follows;

where;
 is mass of electron = 9.11 x 10⁻³¹ kg
 is mass of electron = 9.11 x 10⁻³¹ kg

Thus, the central force acting on the electron as it revolves in a circular orbit is  .
.
Learn more about centripetal force here:brainly.com/question/20905151