work definition in phisycs

1. Magnitude: Scalar
Input Variables:
Force, Displacement
Formula: 𝐖 = ∓. ∆𝐫

2. WORK 1D
1
2
X
Y
Z
If the body
(blue figure)
moves from
position "1" to
position "2", on
the straight
line (blue color)
we can assume
that the work
is done in 1D.
𝑟1
𝑟2
∆𝑟
𝑟1= Position “1”
𝑟2= Position “2”
∆𝑟= Displacement

3. WORK 1D
The line of
action of the
displacement
vector is the
new axis (x).
And the work
that was done
in space now is
done in one
dimension (1D)
𝑟1
𝑟2
∆𝑟 = ∆𝑥
x
∆r = ∆x = ( x2 - x1 ) 𝑖 is the unit vector of the x-axis𝑖
The cause of the change in object position must be a force ( Fx, that is on the x-axis).

4. Professor
Kowalski

5. Professor
Kowalski

6. WORK 1D
"Work" is
performed by
pushing the
car on a
horizontal
surface.
Force ( Fx)
Displacement
(Dx)
As a result the
car changes
position.
𝑖

7. WORK 1D
X
Work of
Fx
The force and
displacement
vectors have the
same direction.
Then the work is
positive
Displacement = Dx
Force = Fx
Work = Fx . Dx
SI measurement units (N).(m) = (N.m) = (Joule) = (J)
CGS measurement units (dyn).(cm) = (dyn.cm) = (erg)
1 erg = 1x10-7 J

8. WORK 1D
X
EXAMPLE
How much work
is done in a
distance Dx by
the force F?
Displacement = Dx
Force = F
Work = Fx . Dx
W = F Dx Cos(a)F
a
W > 0 W < 0W = 0
a = 0º a = 90º a = 180º

9. Stanley Kowalski. 8.01 Physics I. Fall 2003.
Massachusetts Institute of Technology: MIT
OpenCourseWare, https://ocw.mit.edu.
License: Creative Commons BY-NC-SA.