University:
Felician University
Course:
PHYS-355 | Advanced Topics in Physics
Academic year:

2024
Views:

363

Pages:

2
Author:

domdairech8y

Our original motion equations of and only work under certain conditions. These equations only find the average values of velocity and acceleration respectively. If we need to need to find the final position of an object when its velocity is changing (accelerating) then we need other equations. The additional equations listed here are known as the kinematic equations. Kinematics is the branch of mechanical physics (mechanics) which describes the motion of bodies without consideration of the causes of this motion. We will get into the causes in chapter 4. A man speeding at 40m/s decides to outrun the cops and starts to accelerate at a rate of 2.5m/s 2 for 12 seconds. What is the criminal’s new speed? A man speeding at 40m/s decides to outrun the cops and starts to accelerate at a rate of 2.5m/s 2 for 12 seconds. How far did he travel in this time? Mr. D’s dog Gromit jumped out of a second story window (through the screen) and fell to the ground below. The window is 15 feet high, the acceleration of gravity is 9.8m/s 2 , and there are 3.28 feet in each meter. What was the final velocity of this crazed dog? (True story, don’t worry he’s fine and now he knows about gravity.) A rocket in mid flight is 1500 meters off the ground, it is traveling at 900m/s is accelerating until it reaches 8000m/s, a velocity fast enough to escape earth’s atmosphere which is 55,000 meters thick. What is the rocket’s acceleration? (this is not realistic only because rockets don’t go straight up. They angle east in order to orbit which elongates their distance) It will be important to note that velocities and accelerations can be negative. For instance consider a ball thrown straight up, which will fall back down to your hand. The acceleration of gravity slows the ball down on its way up. The ball momentarily stops and then gravity makes the ball go fast again on its way down. We typically denote up as a positive direction and down as a negative direction, so the initial velocity of the ball when thrown is positive. You can often consider either the ground or your hand to be at a position of zero (depending on which is more convenient) and its peak height will be positive. Since gravity always acts in the downward direction it is negative, and the velocity of the ball when it is on its way back down will also be negative. The acceleration of gravity is a constant -9.8m/s2. A ball is thrown upward from ground level at a velocity of 25m/s. What maximum height will it reach? How long will it take to reach its maximum height? What will be its velocity after 4 seconds? A ball (ball 1) is dropped from a very tall building. One second later another ball (ball 2) is dropped. What are the velocities of the two balls 4 seconds after the first ball is dropped? Ball 1 Ball 2 What is the difference in their velocities? THINK!!!! how this will change with time. find their velocities after 5 seconds to see the change if necessary. How will the distance between the two balls change with time. THINK ABOUT THIS! don’t just assume. Find their distances after 5 seconds to see the change if necessary.