10
(b) v
(6 6)
0
Displacement
v
0m / sec
2 60 sec 120
total time
Caution: if an object doesn‟t change its direction, then speed and velocity are the same.
For convenience, we will drop both the arrow on top of the velocity vector and speed, but will keep the
distinction between speed and velocity.
1.5 Problems Solving Method
One of the objectives of this chapter is to help students learn a procedure for solving problems in science.
The procedure can be outlined in the following:
Read the problem carefully. Read it at least twice, slowly and completely from the beginning to
the end
Make a sketch of the problem if it is necessary. You can substitute or represent any object by a
dot or a box
In your notebook, write down all given information (data) with units. Look at some terms that
carry some information. For example, motion from rest means initial velocity equals zero. Also,
the term „smooth surface‟ indicates no friction
Write down the unknown quantity or quantities the question asked for
Write down the basic equation or formula that relates all the known and the unknown quantities
Find the working equation or formula for the unknown quantity
Substitute the data in the working equation, including the units. Verify your work
The following example illustrates this procedure
Example 1.5
Find the distance traveled by a car travels with an average speed of 80km/hr in 2.0 hr.
Solution:
Sketch:
x
0
d=?
Data (given information): v 80 km / hr , t 2.0hr , wanted: d ?
Basic equation:
Working equation:
Substitute and solve:
v
d
t
d vt
d (80km/ hr ) (2hr ) 160km