4C Physics
Remember GUSS?
This is GUSS
GUSS has a procedure for solving problems.
First, he identifies his
This is GUSS
GUSS has a procedure for solving problems.
First, he identifies his Givens.
Then he identifies his
This is GUSS
GUSS has a procedure for solving problems.
First, he identifies his Givens.
Then he identifies his Unknown.
Next, he
This is GUSS
GUSS has a procedure for solving problems.
First, he identifies his Givens.
Then he identifies his Unknown.
Next, he Selects an equation that relates his
Givens and his Unknown, rearranging it for
the Unknown if necessary.
Finally, he substitutes his Givens into the
equation and
This is GUSS
GUSS has a procedure for solving problems.
First, he identifies his Givens.
Then he identifies his Unknown.
Next, he Selects an equation that relates his
Givens and his Unknown, rearranging it for
the Unknown if necessary.
Finally, he substitutes his Givens into the
equation and Solves for his Unknown.
Let’s Practice. . . .
Identify the Givens and the Unknown in
the following problem:
A machine did 240 J of work in 60 s.
Calculate its power output.
Let’s Practice. . . .
A machine did 240 J of work in 60 s.
Calculate its power output.
This is not an adequate identification and
will not earn you part marks:
Let’s Practice. . . .
A machine did 240 J of work in 60 s.
Calculate its power output.
This will:
Note that all Givens have been assigned
variables.
Let’s Practice
When you Select an equation, you are
selecting the equation that contains
those variables.
The equation that contains W, Dt, and P is:
W
P
Dt
Let’s Practice
W
P
Dt
This equation does not need to be rearranged.
It is already solved for our unknown.
Let’s Practice
W
P
Dt
This equation does not need to be rearranged.
It is already solved for our unknown.
But what if you needed to solve for W or Dt?
Rearranging Equations
If you want to solve for W, you need to get rid
of anything on the same side as the W.
W
P
Dt
W 
PD t    Dt
 Dt 
PDt  W
or W  PDt
Rearranging Equations
If you want to solve for W, you need to get rid
of anything on the same side as the W.
To get rid of a division, use multiplication:
W
P
Dt
W 
PD t    Dt
 Dt 
PDt  W
or W  PDt
Rearranging Equations
If you want to solve for W, you need to get rid
of anything on the same side as the W.
To get rid of a division, use multiplication:
W
P
Dt
W 
PD t    Dt
 Dt 
PDt  W
or W  PDt
Rearranging Equations
If you want to solve for W, you need to get rid
of anything on the same side as the W.
To get rid of a division, use multiplication:
W
P
Dt
W 
PD t    Dt
 Dt 
PDt  W
or W  PDt
Rearranging Equations
If you want to solve for W, you need to get rid
of anything on the same side as the W.
To get rid of a division, use multiplication:
W
P
Dt
W 
PD t    Dt
 Dt 
PDt  W
or W  PDt
Rearranging Equations
If you want to solve for Dt, you first need to get
it out of the denominator
W
P
 PDt  W
Dt
PDt W

P
P
W
Dt 
P
Rearranging Equations
If you want to solve for Dt, you first need to get
it out of the denominator and then get rid of
anything on the same side as it.
W
P
 PDt  W To get rid of
Dt
multiplication,
PDt W use division.

P
P
W
Dt 
P
Rearranging Equations
If you want to solve for Dt, you first need to get
it out of the denominator and then get rid of
anything on the same side as it.
W
P
 PDt  W To get rid of
Dt
multiplication,
PDt W use division.

P
P
W
Dt 
P
Rearranging Equations
If you want to solve for Dt, you first need to get
it out of the denominator and then get rid of
anything on the same side as it.
W
P
 PDt  W To get rid of
Dt
multiplication,
PDt W use division.

P
P
W
Dt 
P
The Last Step
Finally substitute your Givens including
units and Solve.
Your solution must also contain units!
W 240J
J
P

4
Dt
60 s
s
The Last Step
Finally substitute your Givens including
units and Solve.
Your solution must also contain units!
W 240J
J
P

4
Dt
60 s
s
or 4 W
since a Joule/second is equal to a Watt.
More Practice
Complete the attached “More Practice with
GUSS” Questions.
“Yay! More Practice with me!
I’m so much fun!”