# Homework Help: How do you devrive equations in kinematics

1. Aug 27, 2009

### DARTZ

Okay, I really need to know exactly how to derive these formulas

(delta)x = (average)v*t

(average)v = v(subscript)f + v(subscript)i/2

a = v(subscript) - v(subscript)i/t

My physics teacher says you can use these 3 formulas to answer any one dimension kinematics problem if the acceleration is constant. Now how do I derive these to get the formula. Please help I am very desperate and I need to know soon.

2. Aug 27, 2009

### rock.freak667

Well distance=speed*time and acceleration is defined as the rate of change of velocity per unit time or (change in velocity)/time

3. Aug 27, 2009

### Andrew Mason

These formulae are only valid if you have constant acceleration. You can derive these without calculus (well, you are using calculus but it is simple geometry) by plotting a speed vs. time diagram of an object moving with constant acceleration.

What does the area under the graph represent? (hint: area = height x width; height = v and width = $\Delta t$). How does the area relate to the maximum and minimum speeds? (think area of a triangle).

AM