CALCULATING FORCES OF MOTION

The trouble with facts is that there are
so many of them.
{HYPERLINK "/quotes/Samuel_McChord_Crothers/"}
Samuel McChord Crothers
, The
Gentle Reader

Whenever we work on solving any motion problems we will be
working with an equation that requires a stepbystep method.

Careful attention needs to be
paid to writing out the known and
unknown measurements, the SI
units involved, and the entering
of numbers into your calculator.
Double check all work!

No need to ask the question "Do we have to show all of our work?"
The unqualified answer to that question is
YES
!
Numbers mean nothing in measurements and science calculations
if they are not labeled with some type of unit.
Physics problems mean nothing without proof of your answer and that comes with writing out the equation. So let's get to it! 
SPEED and VELOCITY EQUATION:
speed = distance OR v = d
time
t

Remember that the SI unit for speed and velocity is meters per
second (m/s). Velocity answers also require a direction.
The best way to learn the steps is to work through a problem. If you need to review solving one step equations, click on the link below. 
Problem
: What is the speed of a sailboat that is traveling
100 meters in 120 seconds?

Step 1
: Write down the equation you need to solve the
problem.

v = d
t

Step 2
: Place the known
information into the
equation.

Known
: The sailboat traveled a
distance of 100 meters and the time
it took to travel that distance was 120
seconds. Since meters per second
is the SI unit for speed, there is no
need for conversions in this problem.
v = 100m =
120 s

Step 3
: Solve. Carefully enter the
numbers into your calculator.
Remember that this is a division
problem. Check to make sure that your
solution contains the correct SI unit.

SOLUTION : The sailboat has a speed of .83m/s. 
One more example problem and then you will practice on your own.

Problem
: If a cyclist in the Tour de
France traveled southwest a distance of
12,250 meters in one hour, what would
the velocity of the cyclist be?


Step 1
: Write down the equation needed for the problem.

v= d
t

Step 2
: Enter all the known values into
the equation, taking care to make all
necessary conversions.

v = 12,250 m =
3,200s

Step 3
: Use your calculator to
solve the problem. Check to
make sure that you included the
correct SI unit and direction.

SOLUTION
:
3.83 m/s southwest

PRACTICE PROBLEMS
:
1. Calculate the speed of a dog running through a field if he is covering 23.7 meters in 54 seconds. 2. If a cross country runner covers a distance of 347 meters in 134 seconds what is her speed? 3. What is the speed of a baseball that travels 49 meters in 2.4 seconds? 4. What is the speed of a horse in meters per second that runs a distance of 1.2 miles in 2.4 minutes? 5. Calculate the velocity of a car that travels 556 kilometers northeast in 3.4 hours. Leave your answer in kilometers per hour. 6. If the distance covered by a jogger is 2,541meters through the park and the time it took to cover that distance was 43.6 minutes, what was the speed of the jogger? 7. Which object has a greater velocity, a ball rolling down a 3.4 meter hill in six seconds or a fish swimming upstream and covering 5.4 meters in 0.4 minutes? 8. If Seneca decides to walk across town to a store that is .95 kilometers away and she has only 25 minutes to get there, what speed does she need to maintain to arrive on time? 9. If a projectile flies north 387 meters in 5.8 seconds, what is its velocity? 10. Calculate the velocity of a mountain climber if that climber is moving northeast at a pace of 1.6 km in 1.4 hours? Give your answer in the SI unit for velocity. 