Answer:
a)
two like charges always repel each other while two unlike charges attract each other. Since the spring stretches by 0.039 m, the charges have the same sign. both charges are positive(+) or Negative (-)
b)
both q1 and q1 are 8.35 × 10⁻⁶ C or  -8.35 × 10⁻⁶ C
Explanation:
 Given that;
L = 0.26 m 
k = 180 N/m
x = 0.039 m 
 
a) 
we know that two like charges always repel each other while two unlike charges attract each other. Since the spring stretches by 0.039 m, the charges have the same sign.
b)
Spring force F = kx
F = 180 × 0.039 
F = 7.02 N
Now, Electrostatic force F = Keq²/r²
where r = L + x = ( 0.26 + 0.039 )
we know that proportionality constant in electrostatics equations Ke = 9×10⁹ kg⋅m3⋅s−2⋅C−2
so from the equation; F = Keq²/r²
Fr² = Keq²
q = √ ( Fr² / Ke ) 
we substitute
q = √ ( 7.02 N × ( 0.26 + 0.039 )² / 9×10⁹ )
q = √ ( 7.02 N × ( 0.26 + 0.039 )² / 9×10⁹ )
q =  √ (0.627595 / 9×10⁹)
q = √(6.97 × 10⁻¹¹)
q = 8.35 × 10⁻⁶ C
Therefore both q1 and q1 are 8.35 × 10⁻⁶ C or  -8.35 × 10⁻⁶ C
 
        
             
        
        
        
Answer:
Fluid fricton goes to Static friction and sliding friction goes to rolling friction
Explanation:
 
        
                    
             
        
        
        
Explanation:
It is given that,
Frequency of the laser light, 
Time,  
 
(a) Let  is the wavelength of this light. It can be calculated as :
 is the wavelength of this light. It can be calculated as :



or

(b) Let n is the number of the wavelengths in one pulse. It can be calculated as :


n = 13440
Hence, this is the required solution.
 
        
             
        
        
        
Answer:
the work done by the lawnmower is 236.14 J.
Explanation:
Given;
power exerted by the lawnmower engine, P = 19 hp
time in which the power was exerted, t = 1 minute = 60 s.
1 hp = 745.7 watts
The work done by the lawnmower is calculated as follows;

Therefore, the work done by the lawnmower is 236.14 J.
 
        
             
        
        
        
It will land in your lap because there's different frames of motion relative to yourself. For example, if you're running at a speed of 6 mph, it doesn't mean you'll run as fast as the Earth spins. Also, since you're on the interior of the plane, any kind of wind or weather on the outside will not affect the coin. A law to back up this claim is Einsteins Special Law of Relativity.