A boat that points straight across a river does not land straight across. In this course we describe the position, velocity and acceleration of a body that moves in a plane, we find that the two directions of motion do not disturb each other, and we use the relative velocity to solve problems about boats in rivers, rain and an umbrella, and aeroplanes in the wind.
3 lessons, about 1 h 20 min3 simulations12 problems6 practice questionsPython in every lesson
The position of a body in a plane is , and its displacement is the change . Average velocity is . As shrinks, it becomes the velocity , which always points along the tangent to the path. Acceleration is the rate of change of velocity, so a turn at a steady speed is an acceleration too.
With a steady acceleration, and . Each equation splits into an equation and a equation, which run side by side with the same time. The path is a straight line or a parabola.
The velocity of A relative to B is . A boat's velocity over the ground is its velocity in the water plus the river's velocity. It crosses fastest when it points straight across, and lands straight opposite only by pointing upstream. Rain seems to slant towards you when you walk, so you tilt your umbrella forward.
Log in to join the discussion.
Loading…