# Homework Help: Position of body

1. Mar 22, 2016

### foo9008

1. The problem statement, all variables and given/known data

for part b , why when t = 0 , x= 0 , why not x =100 ? the author gave that the object drop from height of 100ft at the start of the question.
2. Relevant equations

3. The attempt at a solution

#### Attached Files:

File size:
36.9 KB
Views:
66
• ###### DSC_0531.JPG
File size:
27.6 KB
Views:
63
2. Mar 23, 2016

### Staff: Mentor

The author is defining the point at which the object is dropped as x = 0, and the point on the ground as x = 100.

3. Mar 23, 2016

### foo9008

Is it wrong to consider x=100 when t=0??

4. Mar 23, 2016

### Staff: Mentor

Yes, if you're trying to follow the author's work.

5. Mar 23, 2016

### HallsofIvy

There are no "coordinates", x, y, t, etc. automatically given by a physical situation- you define those yourself. Here, where we have an object dropped from a height we can choose to take x to be 0 at the ground, in which case x(0)= 100, or we can choose to take the x to be 0 at the point from which the object was dropped so that x(0)= 0. We can also choose in which direction to take x to be positive or negative.