Hewitt Drew-It! PHYSICS Screencasts
Linear Motion

8. Linear Motion Definitions

(Paul links central kinematic definitions and equations to Barry Biker.)

End Question: Suppose that Barry Biker, with his motor off, coasts down a hill from rest. He moves at a smooth, small, and constant acceleration. In 4 seconds he reaches a speed bump while moving at 12 m/s. What is the distance between his starting point and the speed bump he encounters? In short, how far does Barry travel in 4 seconds?

9. Bikes-and-Bee Problem

(Paul shows a simple solution to a classic problem involving the motion of a bee that flies to-and-fro between approaching bikes.)

End Question: If the two bikes traveled at twice the speed, 20 km/h, how many kilometers would the bee travel before being squished?

10. Unit Conversion

(Paul discusses unit conversion by means of cancellation, illustrated with a simple average-velocity problem featuring Fast Freda.)

End Question: If you closed your eyes for twice as long as 0.70 seconds, how much farther in distance would you travel at the same speed of 100 km/h. Defend your answer with an equation.

11. Velocity Vectors

(Paul extends a televised classroom lecture on vectors to explain the resultant velocities of airplanes in wind.)

End Question: Suppose our airplane with a normal ground speed of 100 km/h is caught in storm where it encounters a 90° crosswind also of 100-km/h.  How fast will the airplane travel across the ground below?

And another question: If the airplane changes course and flies directly into the 100 km/h wind, what will be its speed relative to the ground below?

12. Free Fall

(Paul investigates and develops free-fall equations as Phil Physiker drops a boulder, with a speedometer attached, from a high cliff.)

End Question: We’ve talked about free fall in a short four-second interval. Question 1) What will be the speed of the boulder when it has fallen for 5 seconds? 2) How far from the top will it have fallen in 5 seconds? 3) What will be its acceleration at the 5th second?