Answer:
f =-20 cm
Explanation:
Given that,
The magnification of a spherical mirror, m = -1
The image distance, v = 40 cm (for negative magnification)
The magnification of a concave mirror is negative. The mirror showing -1 magnification is a concave mirror.
Let f be the focal length of the mirror. We know that,

Object distance, u = -40 cm
Using mirror's formula i.e.

So, the focal length of the mirror is 20 cm.
Answer:Newton's 2nd law
Explanation:Newton's 2nd law also states that the rate at which an object changes speed is proportional to the force that is exerted. Engines provide thrust and accelerate a plane forward along the runway. If the engines supply a small force, only a small acceleration will result.
If the gravity decreases on the earth, we will be weightless and pressure will be less exerting on us and we will be able fly
According to Lindemann's 10 percent law, only 10% energy transferred from one trophic level to the next.
In short, Your Answer would be 10%
Hope this helps!