PHYS133 Chapter Notes - Chapter 4: Orbital Speed, Trick-Trick, Weightlessness

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amethystferret441

3 Mar 2016

School

University of Delaware

Department

Physics and Astronomy

Course

PHYS133

Professor

Mullan Dermott

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Document Summary

Precise definition to describe motion: speed: rate at which object moves (speed = distance/time in meters/sec, velocity: speed and direction (10 m/s due east, acceleration: any change in velocity. Mass m; the quantity of matter in an object (molecules) Weight the force f that acts on an object due to gravity: f= m x g (when g is the force of gravity) On earth, all masses are attract4ed downwards with a force f= m x g(e) G(e)= the acceleration due to gravity on earth. On the moon, g is smaller: g(m) =g(e)/6. When does weight change you are weightless in free fall, you"re weight is lower when you start going down in an elevator. All falling objects on earth accelerate and the same rate (not including friction of air resistance) On earth, g is about 10 m/s^2: speed increases 10 m/s with each second of falling. Suppose object accelerates at rate a meters/second/second.

Related Questions

Galileo thought about whether acceleration should be defined as the rate of change of velocity over time or as the rate of change in velocity over distance. He chose the former, so let’s use the name “vroomosity” for the rate of change of velocity over distance. For the motion of a particle on a straight line with constant acceleration, the equation v = v_i + at gives its velocity v as a function of time. Similarly, for a particle’s linear motion with constant vroomosity k, the equation v = v_i + kx gives the velocity as a function of the position x if the particle’s speed is v_i at x = 0. (a) Find the law describing the total force acting on this object of mass m. Describe an example of such a motion or explain why it is unrealistic for (b) the possibility of k positive and (c) the possibility of k negative.

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(a) An elevator of mass m moving upward has two forces acting on it: the upward force of tension in the cable and the downward force due to gravity. When the elevator is accelerating upward, which is greater, T or w? (b) When the elevator is moving at a constant velocity upward, which is greater, T or w? (c) When the elevator is moving upward, but the acceleration is downward, which is greater, T or w? (d) Let the elevator have a mass of 1500 kg and an upward acceleration of 2.5 m/s². Find T. Is your answer consistent with the answer to part (a)? (e) The elevator of part (d) now moves with a constant upward velocity of 10 m/s. Find T. Is your answer consistent with the answer to part (b)? (f) Having initially moved upward with a constant velocity, the elevator begins to accelerate downward at 1.50 m/s². Find T. Is your answer consistent with the answer to part (c)?