Tiêu đề 13 Motion Problem.pdf ✅

MSTC 13: Motion Problems The average speed of an object is the ratio of its distance traveled over some time. In symbols, speed = distance time v = d t From this relation, the speed is directly proportional to the distance and inversely proportional to time. The speed is higher if more distance is covered in the same amount of time. The speed is higher if less time is consumed in covering the same distance. Also, distance and time are directly proportional to each other. More time is needed to cover more distance if the speed is constant. Usual units are m/s and kph in S.I. and ft/s and mph in the English units. (See conversions in MSTC 1: Units Conversion). Some factors can either assist or impede the motion of an object. Imagine a boat in a river. In still waters, the speed of the boat is the only one propelling it. However, if the river flows, the boat can either speed up or slow down depending on its direction relative to the current. The direction of the boat is said to be upstream when it moves "against" the current and downstream when it moves "with" the current. This concept is also applicable to planes moving with or against the wind. Wind moving in the direction “against” a plane is called headwind, and wind moving “with” the plane is called tailwind.