Physics Questions

Black  surfaces are good emitters of heat ( They are also good absorbers of heat). If the black surface is rough too, the emitting will be better. So (b) is the correct answer. Shining surfaces reflect back radiation. So if the black surface is also shining the effectiveness of emitting heat is lessened.

It is to overcome this opposite frictional force , that  we have to apply the needed force to make the body move

Phototropism is the ability of a photosynthesizing organism, to grow directionally in response to a light source. It is very common in plants, but can also occur in other organisms such as fungi.

Example :: Sunflower

$$\begin{gathered} 32oF \\ We know that \\ T(°F) = T(°C) × 1.8 + 32 \\ 32(°F) = 0(°C) \end{gathered}$$