Datasheet

Page 26· Applied Robotics with the SumoBot
These unit conversions take some practice; here are some tips:
√ Find the equality with your desired result units first.
√ Make it a conversion factor with the desired units in the numerator.
√ Find equalities with units that link your starting units to your result units.
√ To make them fractions equal to 1, start by making sure that the denominator of
your first fraction cancels the units of the value you are starting with.
√ Repeat that until you get to the desired result.
Friction Forces
Figure 1-8 shows the forces at work if you try to slide an object like a block along a flat
surface like a table. The arrows are called vectors, and they indicate the magnitude and
direction of the forces applied. The (W) vector in Figure 1-8 indicates gravity's action on
the book's mass, a downward force on the table. The table responds with an equal and
opposite force, which is typically labeled (N) for normal force. In this case, the term
normal has a special meaning - it's the force that's perpendicular to the contact surface,
and it prevents the block from falling through the table. (F) is the force applied that tries
to slide the block along the table. The forces of friction between the block and the table
(f
S
or f
k
) cause the table to oppose the applied force that's trying to make the block slide.
If you're not pushing hard enough to make it slide, the force comes from static friction
(f
S
). If you have pushed hard enough to overcome the force of static friction and the
block starts moving, the slightly weaker force of kinetic friction (f
K
) takes over.
Figure 1-8
Forces Acting on an
Object
Forces of friction that
result from pushing
an object along a
level surface
kg2268.0
g1000
kg1
lb1
g6.453
oz16
lb1
oz8
111oz8oz8
=
×××=
×××=