Physics 105 max.byu.edu website Schedule Reading reports (1 and 2 due tonight) Homework (1-3 due Sat) Clickers Exams-see syllabus

Kinematics mathematical description of motion (1-D for now) position x(t) velocity v(t) acceleration a(t)

Motion concepts you already know distance traveled time average speed: distance/time these are scalars

New vector definitions for physics displacement average velocity (vs speed) 1D: these have signs that show direction: e.g. + to right, - to left

On the Tour de France Lite, bicyclists ride straight south, 8 km/hr for 3 hours, rest for 2 hours, and ride down a mountain south 20 km/hr for 1 hour. What were the average speed and the average velocity for the morning? After a one hour rest, they go back up (north) the 20 km downhill part in 2 hours. Their average velocity for the whole day is [P2]__________ km/hr A: 7.11 B: 3.24 C: 2.67 D: E: 5.85 in the direction [P3] ______ A) north B) South Their average speed for the day was [P4] _________ km/hr A: 7.11 B: 3.24 C: 2.67 D: E: 5.85

Position graph x(t) We choose a coordinate system with origin Positive x means: Negative x means: Zero x means: Left-right position of a roller coaster

Find instantaneous v at 6 seconds in m/s, including direction.

Left-right position of a roller coaster During the ride the roller coaster stops and turns around [P5] _____ times. A: 1 B: 2 C: 3 D: 4 E: 5..

Left-right position of a roller coaster The time is it going the fastest is closest to the time [P6]______ sec. A: 4 B: 6 C: 8 D: 10 E: 12 At t = 7 sec, the car is moving to the [P7]______ A: right B: left C: not moving.

Sketch v(t) from the slope of x(t)

Famous train problems! A train leaves Provo for SLC at 8:00 am, going 10 mph. A second express train leaves Provo for SLC at 9 am, going 15 mph. It is 40 miles to SLC. Will the 2 nd train catch up before SLC? Where? If someone on the first train looks back and sees the second train getting closer, with what speed does the gap between them narrow? This is the magnitude of the relative velocity (difference in velocities).

Lecture 1, HW1 Velocity Basic concepts: ◦moving left/right from x(t) graph ◦speeding up, slowing down from v(t) graph Basic problems: ◦finding displacement, speed, average velocity Advanced concepts: ◦speeding up, slowing down from x(t) graph Advanced problems: ◦relative velocity, two objects “meeting” or catching up

A car moves along a road. There is a lamp post at x = 0. Which x vs t curve describes: P8. slows down as it moves away from the lamppost P9. moves toward the lamppost then turns around P10. a car speeding up as it moves toward the lamppost P11. a car that moves away from the lamppost, turns around and passes the lamppost