Answer:
The separation between the charges was decreased by a factor of 0.2
Explanation:
The Coulomb's force between two charges is given by;

r₂ = 0.2r₁
Therefore, the separation between the charges was decreased by a factor of 0.2.
(a) 
<u>Explanation:</u>
Given:
Moment of Inertia of m₁ about the axis, I₁ = m₁x²
Moment of Inertia of m₂ about the axis. I₂ = m₂ (L - x)²
Kinetic energy is rotational.
Total kinetic energy is 
Work done is change in kinetic energy.
To minimize E, differentiate wrt x and equate to zero.

Alternatively, work done is minimum when the axis passes through the center of mass.
Center of mass is at 
Answer:
v = 7.67 m/s for L= 1m
Explanation:
Let's use the conservation of mechanical energy, at the highest point and the lowest point
Initial. Vertical ruler
Em₀ = mg h
Final. Just before touching the floor
= K = ½ I w²
Em₀ = 
m g h = ½ I w²
The moment of inertia of a ruler that turns on one end is
I = 1/3 m L²
Let's replace
m g h = ½ (1/3 m L²) w²2
g h = 1/6 L² w²
They ask for the speed of the end so the height h is equal to the length of the ruler
g L = 1/6 L² w²
The linear and angular variables are related
v = w r
w = v / r
In this case the point of interest a in strangers r = L
g L = 1/6 L² v² / L²
v = √ 6 g L
Let's calculate
Assume that the length of the meter is L = 1 m
v = √ (6 9.8 1)
v = 7.67 m/s
Answer:

Explanation:
From the vertical movement, we know that initial speed is 0, and initial height is H, so:

solving for t:

Now, from the horizontal movement, we know that initial speed is V and the acceleration is -g/4:
Replacing values:

Simplifying:

Answer:
109.66km
Explanation:
Velocity is defined as the change in displacement of a body with respect to time.
Velocity = displacement/Time
Displacement = velocity * time
A truck is traveling due north at 75 km/hr approaching a crossroad and perpendicular road a police car is traveling west toward the intersection at 80 km/hr, then the resultant velocity is gotten using the pythagoras theorem since they are both perpendicular to each other.
v² = 75²+80²
v² = 5625+6400
v² = 12,025
v = √12,025
v = 109.66km/hr
If both vechicles reaches cross road in exactly one hour, the displacement of the truck with respect to the police car = 109.66km/hr * 1 hour
Displacement of the truck with respect to the police car = 109.66km