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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.

Lectures.
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