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PHYS 284 Lecture Notes - Lecture 4: Distant Star, Net Force, Food Energy

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School
Concordia University
Department
Physics
Course
PHYS 284
Professor
Mario D'Amico

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Document Summary

Speed: a car tells us how far it will go in a certain amount of time. Velocity: a car tells us both its speed and its direction. Acceleration: a car has an acceleration of its velocity is changing in any way, whether in speed or direction of both. Constant velocity: direction is changing but speed remains constant. One of the most important types of acceleration is acceleration caused by gravity. Air resistance causes the difference of gravity in acceleration (feather/rock). Acceleration of gravity: is the acceleration of a falling object. On earth the acceleration of gravity causes falling objects to fall faster by 9. 8 meters per second (m/s) or about 10 m/s with each passing second. E. g. dropping a rock from a tall building. When you first drop it, it will be 0 m/s, after 1 second the rock will be falling downward at 10 m/s, after 2 seconds it will be falling at 20 m/s.

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Related textbook solutions

Physics: Principles with Applications
7th Edition, 2013
Giancoli
ISBN: 9780321625922

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Related Questions

The figure shows three graphs, A, B, C, which collectively describe the motion of an object in one dimension. The horizontal axis of each graph is time (symbol t). The vertical axes of the graphs are different. For one graph the vertical axis is position (symbol x), for another, it is the velocity (symbol v), and for another, it is acceleration (symbol a). Where the axes across is the point of zero for both time and the quantity corresponding to the vertical axis. Part A: For which sequence of graphs is the vertical coordinate position, velocity, and acceleration, respectively? (e.g., If you think graph Y is position versus time, graph X is velocity versus time, and graph Z is acceleration versus time, then your answer is Y, X, Z.). Multiple choice: 1)C, A, B 2)A, C, B 3)C, B, A 4)B, C, A 5)B, A, C 6)A, B, C. Part (b) Which one of the following situations can be most accurately represented by the graph, consistent with your answer to part (a)? (1) A car driving in the negative x-direction suddenly shifts into reverse and, with tires spinning, slows to a momentary stop before beginning to move in the position x-direction. (2)A car driving in the position x-direction slams on its brakes and comes to rest. (3) A rock is dropped from the rest from the top of a tall building. Assume air drag can be neglected, in which case its speed increases by the same amount each second. Take upward to be the position x-direction. (4) A sprinter runs a 100-meter dash and she runs in the negative x-direction. Starting from rest, she has a constant acceleration for the first 50 meters, then a constant speed for the remaining 50. Multiple choices: 1)4, 2)3, 3)2, 4)1.

1. If an object moves with constant acceleration, its velocity a) must be constant also b) always decrease c) increases by the same amount each second  d)change by varying amount depending on its speed.

2. A man leans over the edge of a cliff and throws a rock upward at 4.9 m/s. Neglecting air resistance, two seconds later the rock's speed is a) 9.8 m/s  b) 14.7 m/s c) 4.98 m/s d) zero e) none of the above

3. Twelve seconds after starting from rest, an object falling freely will have a speed of a) 10 m/s b) 50 m/s c) more than 100 m/s d)100 m/s.

4. A ball is thrown 125 meters upward and then falls the same distance back to Earth. Neglecting air resistance, its total time in the air is about 10 seconds. about 15 seconds. about 5 seconds. more than 20 seconds. 

A relief airplane is delivering a food package to a group of people stranded on a very small island. The island is too small for the plane to land on, and the only way to deliver the package is by dropping it. The airplane flies horizontally with constant speed of 260 at an altitude of 1000 . The positive x and y directions are defined in the figure. For all parts, assume that the "island" refers to the point at a distance from the point at which the package is released, as shown in the figure. Ignore the height of this point above sea level. Assume that the acceleration due to gravity is = 9.80 . After a package is ejected from the plane, how long will it take for it to reach sea level from the time it is ejected? Assume that the package, like the plane, has an initial velocity of 260 in the horizontal direction. If the package is to land right on the island, at what horizontal distance from the plane to the island should the package be released? What is the speed of the package when it hits the ground?