Answer:
0.8 seconds
Explanation:
F=ma
Let x be the seconds the force is applied.
m = 20kg
F = 50 Newtons (kg*m/sec^2)
acceleration, a, is provided for x seconds to increase the speed from 1 m/s to  3 m/s, an increase of 2m/s
Let's calculate the acceleration of the cart:
F=ma
(50 kg*m/s^2) = (20kg)*a
a = 2.5 m/s^2
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The acceleration is 2.5 m/s^2.  The cart increases speed by 2.5 m/s every second.  
We want the number of seconds it takes to add 2.0 m/sec to the speed:
(2.5 m/s^2)*x = 2.0 m/s
x = (2.0/2.5) sec
x = 0.8 seconds
 
        
             
        
        
        
Answer:
f = 1.18 x 10¹¹ Hz
Explanation:
The equation used to find frequency is:
f = c / w
In this form, "f" represents the frequency (Hz), "c" represents the speed of light (3.0 x 10⁸ m/s), and "w" represents the wavelength (m).
Since you have been given the value of the constant (c) and wavelength, you can substitute these values into the equation to find frequency.
f = c / w                                                      <---- Formula
f = (3.0 x 10⁸ m/s) / w                                 <---- Plug 3.0 x 10⁸ in "c"
f = (3.0 x 10⁸ m/s) / (2.55 x 10⁻³ m)            <---- Plug 2.55 x 10⁻³ in "w"
f = 1.18 x 10¹¹ Hz                                         <---- Divide
 
        
             
        
        
        
Your list of choices is a very short list, and doesn't include any 
correct explanation.
The mass of an atom is roughly the number of protons AND neutrons 
in its nucleus, but the element only depends on how many protons are there.  
Different atoms of the same element may have different numbers of 
neutrons, so their masses are different.  But they're the same element, 
because they all have the same number of protons.
        
             
        
        
        
Answer:
100
Explanation:
take note that v=d/t (velocity is distance over(divided by) time, so in this case it would be 200 (distance) divided by 2 (time) = 100
 
        
             
        
        
        
Answer:
When an object is balanced, about a pivot, the total clockwise moment must be equal to the total anticlockwise moment about that pivot.
Hope that helps.