It is a vector that doesn't follow vector laws.

A quantity that doesn't obey vector laws cannot be considered a vector.

Tension (or compression) in general is not a force but a pair of equal and opposite forces acting at a certain point. In problems in Physics and engineering, we often consider only one of the two forces in the tension pair and call it tension or tensile force. In this way, we can consider tension as a vector.

When you go by the layperson's definition of a tensor in Physics that says, "tensor is a physical quantity which has one magnitude and multiple directions.", you may consider tension as a tensor. However, tension does not fit the mathematical matrix in order to be a mathematical tensor. This is why the layperson's definition of a tensor isn't a valid one.

I hope my explanation helps.

]]>Here is the video of how a javelin flies.

]]>Although the question does not explicitly state it, we can assume the following:

The object is moving towards the mirror at a velocity $2\ \frac{m}{s}$ with respect to the ground and the mirror is moving towards the object at a velocity $3\ \frac{m}{s}$.

When all distances are measured from the centre of the mirror, let object distance be $u$ and image distance be $v$. We also have to follow the sign convention. However, to provide an easy and intuitive answer, let is also assume that the mirror is a plane mirror.

**For plane mirrors:**

It is well established that $v=u$ (ignoring the sign).

Thus the time rate of change of $v$ must be the same as the time rate of change of $u$.

$\frac{dv}{dt}=\frac{du}{dt}$.

To correctly find the value of $\frac{du}{dt}$, we have to consider the mirror to be at rest with us. Hence the object velocity now becomes relative to the mirror. Since the object and the mirror are moving towards each other, the magnitudes must be added.

Then, with respect to the mirror (and thus to us),

$\frac{dv}{dt}=\frac{du}{dt}=2+3=5\ \frac{m}{s}$.

This means that the image is also moving towards the mirror at a velocity $5\ \frac{m}{s}$, with respect to the mirror. Thus the image velocity with respect to the ground is $8\ \frac{m}{s}$. (Answer)

**Steps for spherical mirrors:**

- Use the mirror equation: $ \frac{1}{u}+ \frac{1}{v}= \frac{1}{f}$.
- Use coordinate sign convention.
- Assign positive directions along the axis of the mirror.
- Find the object and image distances and velocities WRT the mirror first.
- Add the image velocity WRT the mirror to the mirror velocity WRT the ground to find the image velocity WRT the ground.

Considering a circle (also applies to any closed loop in 2D) to consist of $360^\circ$ is actually convention with the following origin:

The evolution of the calendar system in various ancient cultures had one similarity. They all referred to the motion of the Sun in the sky. The Sun apparently makes a full circle in a year. Most ancient cultures rounded up the number of days in a year to be 360. In the ancient Hindu Vedic calendar system or astrology, there are 30 days in a month and there are 12 months in a year. This inspired the mathematicians to consider the circle to have $360^\circ$. To correct for the discrepancies between the actual 365 days in a year and the 360 days per year in the calendar, they used correctional methods that added an additional month in a certain amount of years.

This convention has lasted for thousands of years for the following reason:

360 is a very convenient number for real-life divisions. For example, 360 is divisible by all the numerical digits from 0 to 9, except for 7. Thus having a circle with a complete angle $360^\circ$^{ }helps us to divide a circle into various parts without writing decimals for the partial angles.

Hope this helps.

Please mark the answer as the right answer if you think so.

Thanks.

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