Answer:
 C
C
Sign-Negative
Explanation:
We are given that 
Electric field = (Radially downward)
 (Radially downward)
Acceleration= (Upward)
(Upward)
Mass of charge=3 g= kg
kg
1kg=1000g
We have to find the magnitude and sign of  charge would have to be placed on a penny .
By newton's second law


Substitute the values then we get 

Substitute the values then we get 




 C
C
Sign of charge =Negative
Because electric force acting  in opposite direction of electric field therefore,charge on penny will be negative.
 
        
             
        
        
        
Answer:
56327040000 metres
Explanation:
1 mile =
1609.344 metres
35000000 miles = x meters
we represent x by the number of meters which the requested miles maps to
we cross multiply, so 1609.344×35000000 = 1 × x
 x =56327040000 metres
 
        
             
        
        
        
Explanation:
0.566kg *(1mol/0.197 kg)= 2.87 mol gold
note how the units cancel out, if the units do not cancel out (kg/kg=1) then u did something wrong
 
        
                    
             
        
        
        
Answer: The area of brick in contact with the floor is 1539  .
.
Explanation:
Given: Length = 19 cm
Width = 9 cm
Height = 9 cm
As the brick is rectangular in shape. Hence, its area will be calculated as follows.

Substitute the values into above formula as follows.

Thus, we can conclude that area of brick in contact with the floor is 1539  .
.
 
        
             
        
        
        
It will be 3 wavelengths because 1 cycle = 1 wavelength.