<u>Answer:</u>
<em>The average speed of the car is 66.9 km/h</em>
<u>Explanation:</u>
Here distance covered with the speed <em>57 km/h=7 km </em>
distance covered with the speed of <em>81 km/h=7 km</em>
<em>Average speed is equal to the ratio of total distance to the total time.
</em>
<em>total distance= 7 + 7= 14 km </em>
<em>
</em>
<em>time taken to cover the first 7 km= 7/57 h </em>
<em>time taken to cover the second part of the journey = 7/81 h
</em>
<em>average speed =
</em>
<u><em>Shortcut:
</em></u>
<em>When equal distances are covered with different speeds average speed=2 ab/(a+b) where a and b are the variable speeds in the phases.
</em>
Answer:
this is impossible for me
Explanation:
The electrostatic potential energy, U, of one point charge q at position d in the presence of an electric field E is defined as the negative of the work W done by the electrostatic force to bring it from the reference position d to that position

Thus, to double the electric potential energy U we need to reduce the distance of separation by half (1/2) because they are inversely proportion
Answer:
meter, kilogram
Explanation:
Here we want to know how big the tiger is. This means that we want to measure its size and possibly its mass.
The size is actually a measure of the length of the tiger, and length is measured in meters.
The mass of an object, instead, is a measure of the "amount of matter" in the substance, and it is measured in kilograms.
The other options are wrong because:
- The second is the unit of time
- The candela is the unit of the luminous intensity
- The mole is the unit of the amount of substance, and it is used for gases
- The ampere is the unit of the current