Answer:
40 cm
Explanation:
We are given that
Magnification of concave mirror, m=4
Object distance, u=-10cm
We have to find the position of image.
We know that
Magnification of concave mirror, m=
Using the formula




Hence, the image is formed at distance 40 cm behind the mirror.
Answer:

Explanation:
According to the Principle of Energy Conservation and the Work-Energy Theorem, the bullet has the following expression:


![F\cdot \Delta s = \frac{1}{2}\cdot m \cdot [v_{A}^{2}-v_{B}^{2}]](https://tex.z-dn.net/?f=F%5Ccdot%20%5CDelta%20s%20%3D%20%5Cfrac%7B1%7D%7B2%7D%5Ccdot%20m%20%5Ccdot%20%5Bv_%7BA%7D%5E%7B2%7D-v_%7BB%7D%5E%7B2%7D%5D)
The average force exerted on the bullet to stop it is:
![F = \frac{m\cdot [v_{A}^{2}-v_{B}^{2}]}{2\cdot \Delta s}](https://tex.z-dn.net/?f=F%20%3D%20%5Cfrac%7Bm%5Ccdot%20%5Bv_%7BA%7D%5E%7B2%7D-v_%7BB%7D%5E%7B2%7D%5D%7D%7B2%5Ccdot%20%5CDelta%20s%7D)
![F = \frac{(7.8\times 10^{-3}\,kg)\cdot [(540\,\frac{m}{s} )^{2}-(0\,\frac{m}{s} )^{2}]}{2\cdot (0.051\,m)}](https://tex.z-dn.net/?f=F%20%3D%20%5Cfrac%7B%287.8%5Ctimes%2010%5E%7B-3%7D%5C%2Ckg%29%5Ccdot%20%5B%28540%5C%2C%5Cfrac%7Bm%7D%7Bs%7D%20%29%5E%7B2%7D-%280%5C%2C%5Cfrac%7Bm%7D%7Bs%7D%20%29%5E%7B2%7D%5D%7D%7B2%5Ccdot%20%280.051%5C%2Cm%29%7D)

Answer:
A
Explanation:
The distance of the object that reflected the sound wave can be calculated by knowing the speed of sound in water and the time interval between transmission and reception of ultrasound.20 Mar 2017