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lecture3

# lecture3 - Ch 2 Kinematics in 1-D Mechanics Kinematics...

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Ch. 2 – Kinematics in 1-D Mechanics Kinematics Dynamics Concepts needed to describe motion w/o forces Deals with the effects that forces have on motion Chs. 2 and 3 Ch. 4 Our goal is to describe the motion of some object. To do this, we must be able to specify its location in space at all times! In other words, what is the position of some object at time t ? Define Displacement : A vector which points from an object’s initial position to its final position.

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In this chapter, we will only consider 1 dimensional motion. Let’s look at the following example : At time t = t a jogger’s position relative to some fixed origin is x At some later At time = o , a jogger s position relative to some fixed origin is o . At some later time, t = t f , her position relative to the origin is x f . What is her displacement during this time interval? t = t o t = t f x origin x o x f Δ x Her displacement, Δ x , is the difference in her initial and final positions. Displacement = Δ x = x f x o Δ x is pronounced “delta x”, or “change in x”. Units? The SI unit of displacement is the meter (m). In 1-D we can also talk about scalar displacement , which is just a number. It can be either positive or negative. For example, in the above problem, if x o = 10 m and x f = 30 m, then her scalar displacement would be positive 20 m.