Download How much force is required to inflate a high pressure

How much force is required to inflate a high pressure bicycle tire to 95 pounds per square
inch (655 kPa) with a hand pump that has a plunger with an area of 5.0 cm2?
Pressure is (P) defined as the ratio of the force (F) exerted per unit surface (A).
One pascal is defined as a force of one Newton per meter squared.
In our case:
P  655kPa  655  10 3 Pa  655  10 3
A  5.0cm 2 
N
m2
1m 2
 5  10 4 m 2
4
2
10 cm
N 

F  PA   655  10 3 2   5  10 4 m 2   327.5N  328 N
m 

An object exerts a force of 500. N and sits on an area of 4.5m X 1.5m. Calculate the
amount of pressure exerted by the object in torr.
Torr is a pressure unit equivalent to a pressure of 133.3 pascals.
Therefore the pressure here is:
F  500 N
A  4.5m  1.5m  6.75m 2
P
F
500 N
N
1torr

 74.1 2  74.1Pa  74 Pa 
 0.556torr
2
A 6.75m
m
133.3Pa
During your travels through deep space you discover a new solar system. You land on the
outermost planet and determine that the acceleration due to gravity is 2.7 m/s^2. If your
mass back on Earth is 72 kg, what force would you exert on a scale in pounds while
standing on the planet's surface?
The force is your weight, which is defined by Newton’s second law to be your mass
times the acceleration (in this case, gravity).
Newton is the force required to move one kilogram with acceleration of 1 meter per
second squared.
Then:
M  72kg
g  2.7
m
s2
F  Mg
F  72kg  2.7
m
kg  m
 194 2  194 N
2
s
s
One pound-force is the force required to move one pound of mass by an acceleration of
9.81 m per second squared (earth’s gravity).
Then, to convert from Newtons to Pound-force we use:
1lbf  1lb  9.81
m
kg
m
kg  m
 1lb  0.453  9.81 2  4.44 2  4.44 N
2
s
lb
s
s
Hence a force of 194N in units of lbf is:
F  194 N 
1lbf
 43.7lbf
4.44 N
As you proceed on to the next planet, some of your unbreakable equipment breaks,
including that top-of-the-line machine which determines acceleration due to gravity.
Calculate the acceleration due to gravity if your 72 kg mass exerts a force of 18 pounds
on the planet's surface.
The force you exert on the surface in Newtons is:
F  18lbf 
4.44 N
kg  m
 79.9 N  79.9 2
1lbf
s
Hence the gravitational acceleration is:
F  Mg
g
F

M
kg  m
s 2  1.11 m
72kg
s2
79.9