2
PHYS 1L03, Winter 2009, McMaster University, R.Nejat
Force on an object
•
A mule and a cart:
– A mule applies a force on a cart, and the cart
applies a force with the same magnitude but
in opposite direction on the mule.
PHYS 1L03, Winter 2009, McMaster University, R.Nejat
What is going on in this picture?
Force
PHYS 1L03, Winter 2009, McMaster University, R.Nejat
• When you kick a ball, your foot exerts a force
on the ball while the two are in contact
1
,
changing the velocity
2
(the speed and/or the
direction) of the ball.
•
1
:--
Force is an interaction between two
objects
.
•
2
:--
Force (external) changes the velocity,
causes acceleration
, of the object.
Force:
PHYS 1L03, Winter 2009, McMaster University, R.Nejat
Brief Review on adding vectors
• If you do not remember how to add
vectors in component form, you
should watch the tutorial video on
vectors posted on AVENUE
• DO NOT SKIP THIS STEP OR YOU
WILL BE LOST FOR THE REST OF
THE TERM!
PHYS 1L03, Winter 2009, McMaster University, R.Nejat
• We can always
break any 2D
vector up into
components
along two
perpendicular
axes, such as x
and y:
θ
Brief Review on adding vectors
PHYS 1L03, Winter 2009, McMaster University, R.Nejat
θ
y
x
A
A
A
r
r
r
+
=
θ
cos
A
A
x
=
sin
A
A
y
=
2
2
2
x
x
A
A
A
+
=
2
2
x
x
A
A
A
+
=
x
y
A
A
=
tan
(
29
y
x
A
A
A
r
r
r
,
=
(
29
y
x
A
A
A
,
=
r
(
29
,
A
A
=
r
Brief Review on adding vectors