William Dwight Whitney The Century Dictionary and Cyclopedia: An
encyclopedic Lexicon of the English Language. (New York: The Century
Co., 1889)4499
Copyright: 2009, Florida Center for Instructional Technology. See
license.

'... radically improved the power, efficiency,
and cost-effectiveness of steam engines'. 'He developed the concept of horsepower,[4] and
the SI unit
of power, the watt,
was named after him.' - Wikipedia

P

=

W/t

=

Fd/t

=

Fv

(watt)

= (J/s)

(N)m/s

Scalar

Ex 1) A force of 40 N is exerted on a
mass, causing it to move with a constant speed of 5 m/s.

What power is
used?

Ex 1) A force
of 40 N is exerted on a mass, causing it to move with a constant
speed of 5 m/s. What
power is used?

P

=

W/t

=

Fd/t

=

Fv

(watt)

= (J/s)

(N)m/s

= Fv = (40 N)(5
m/s)

200 Nm/s

or 200 watts

Ex 2) A girl weighing 500. newtons
takes 50. seconds to climb a flight of stairs 18 meters high.

Her power
output vertically is

Ex 2) A girl weighing
500. newtons takes
50. seconds to climb a flight of stairs 18
meters high. Her power output
vertically is

F = 500. N

t = 50. secs

d = 18 m

P = ?

P

=

W/t

=

Fd/t

=

Fv

(watt)

= (J/s)

(N)m/s

P = Fd/t

P = 500. N(18. m)/50. sec

P = 180 Nm/sec = 180
watts

Ex 3)A 95-kg student climbs 4.0 m up a rope in 3.0
seconds.

What is the power output of the student?

Ex 3)A 95-kg
student climbs
4.0 m up a
rope in
3.0 seconds.
What is the
power
output of the student?