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Video Index for Lecture 2

Lecture 2 - Recorded on September 10, 1999

1-Dimensional Kinematics, Speed, Velocity, Acceleration

Video Lectures: (RM-80K) (RM-300K)

This lecture is an introduction to kinematics which ultimately leads (in Lecture 4) to trajectories in 3 dimensions.


SEG # SEGMENT TITLES SEGMENT TOPICS STARTS AT (MIN:SEC)
1 Introduction to 1-Dimensional Motion Professor Lewin describes 1D motion of a particle. He talks about average velocity, the importance of "+" and "-" signs, and our free choice of origin. 00:00
2 Average Speed vs. Average Velocity The two are VERY different. The average velocity can be ZERO, while the average speed is LARGE. 05:19
3 Instantaneous Velocity Considering the incremental change in position x with time t, we arrive at v=dx/dt. The instantaneous velocity is the derivative of the position with respect to time. Professor Lewin reviews when the velocity is zero, positive and negative; he distinguishes speed from velocity. 06:56
4 Measuring the Average Speed of a Bullet Professor Lewin shoots a bullet through two wires. The average speed can be calculated from the distance between the wires and the elapsed time. All uncertainties in the measurements are discussed; they have to be taken into account in the final answer. 11:05
5 Introducing Average Acceleration The average acceleration between time t1 and t2 is the vectorial change in velocity divided by (t2-t1). 17:35
6 Instantaneous Acceleration The acceleration, dv/dt, is the derivative of the velocity with time. It is the second derivative of the position x with time. Professor Lewin shows how to find the sign of the acceleration from the slope in an x-t plot. 24:46
7 Quadratic Equation of Position in Time When the position is proportional to the square of the time, the velocity depends linearly on time, and the acceleration is constant. 27:24
8 1D Motion with Constant Acceleration Professor Lewin writes down a general quadratic equation for the position as a function of time, and he relates the constants in this equation to the initial conditions at time t=0. The gravitational acceleration is a constant (9.80 m/s^2 in Boston), and it is independent of the mass and shape of a free-falling object, if air drag can be ignored (see Lecture #12). You can use this result to measure g using the free fall time measurements from the falling apples in lecture 1. 34:18
9 Strobing an Object in Free Fall Professor Lewin drops an apple from 3.20 m and takes a polaroid picture of the falling apple which is illuminated by a strobe light. First two light flashes per second, and then ten flashes per second. 41:17