Why do planes shake and sometimes drop when it goes through clouds?
because the air in clouds has different density from clear air, so the varying densities on different parts of the wing and fuselage and changing densities as you go through the cloud causes turbulence. Also, clouds often form at a layer of the atmosphere where winds change - that change in wind can also cause turbulence.
If the clouds are cumuli-form then it is because they are formed by air rising into the atmosphere. The air is moving at different speeds therefore the plane bounces around a little bit. It’s an unstable atmosphere if you see those types of clouds out of the window.
Picture a canoe in a river with rocks, the water flows over the rocks making for a rough ride. The air is very similar but you usually can’t see it moving.
To the little knowledge i know,i know that its the time when hot air rising from the earth into the atmosphere meets cold air .Sometimes you can even experience clear air turbulence(movement of air masses in the absence of any visual cues such as clouds, and is caused when bodies of air moving at widely different speeds meet) which also shakes and drop aircraft. Thank you 