FOUR USES OF CONCAVE MIRROR:Satellite dishes,headlights of a car, telescopes used for astronomical studies, and shaving mirrors because of there curved and reflective surface.
FIVE USES OF LENSES: Camera lens ,microscopes ,magnifying glass,eyeglasses,projector
To calculate the speed and velocity of the Ann`s we use the formula,

Here, d is distance and t is time and v if we take it with direction then it is called velocity and if we take it without the direction then it is called speed.
Given
and
.
Substituting these values in above equation we get

As Ann walked towards south direction therefore, Ann`s velocity is 3 mi/h south and her speed is 3 mi/h .
Answer:

vector with direction equal to the axis X.
Explanation:
We use the Gauss Law and the superposition law in order to solve this problem.
<u>Superposition Law:</u> the Total Electric field is the sum of the electric field of the first infinite sheet and the Electric field of the second infinite sheet:

<u>Thanks Gauss Law</u> we know that the electric field of a infinite sheet with density of charge σ is:

Then:

This electric field has a direction in the axis perpendicular to the sheets, that means it has the same direction as the axis X.
Answer:
Explanation:
Intensity of light is inversely proportional to distance from source
I ∝ 1 /r² where I is intensity and r is distance from source . If I₁ and I₂ be intensity at distance r₁ and r₂ .
I₁ /I₂ = r₂² /r₁²
If r₂ = 4r₁ ( given )
I₁ / I₂ = (4r₁ )² / r₁²
= 16 r₁² / r₁²
I₁ / I₂ = 16
I₂ = I₁ / 16
So intensity will become 16 times less bright .
"16 times " is the answer .
Pulling a dogs leash: inertia