Hydraulics - work, power, energy

1. WORK, POWER AND ENERGY

2. WORK, POWER AND ENERGY
WORK
If an object or system, such
as your body, exerts a force
on an object and that force
causes the object’s position
to change, you are doing
work on the object.

3. WORK
When a physicist is talking about work, he mainly talks about
a force causing a displacement of an object in the same
action of line.
W=F.Δx
W = work = joule (J) (N.m=J)
Δx = displacement = meter (m)
F = force applied = newton (N)
Work done by 8N between KL is 2 joule. Then, what is the distance x?

4. POWER
Power is the measure for how fast the work is done
•A man lifts a weight of 300N through a vertical line with an average
velocity of 1m/s. What is the power of the man?
A horse is pulling a cart with a force of 150 N by 10m is 20 s

5. ENERGY
•Energy is defined as “ability to do work”
We do work by using energy so both work and energy are measured in
joules.

6. The Law of Conservation of Energy
•The energy in a system may
take on various forms such
as thermal, light, electric,
etc… but the energy may
neither be created nor
destroyed.
•Therefore the sum of all
energies in the system is a
constant.

7. Mechanical Energy
•Ability to do work in a system.
•It has two categories which are kinetic energy and potential energy
Kinetic energy
•Kinetic energy is the energy of motion. An object which has motion -
whether it be vertical or horizontal motion - has kinetic energy.
Kinetic energy is a scalar quantityKinetic energy is a scalar quantity; it
does not have a direction unlike velocityKinetic energy is a scalar
quantity; it does not have a direction unlike velocity, accelerationKinetic
energy is a scalar quantity; it does not have a direction unlike velocity,
acceleration, force

8. Kinetic energy depends upon two variables: the
mass (m) of the object and the speed (v) of the
object.
•Determine the kinetic energy of a 1000-kg roller coaster car that is moving with a
speed of 20.0 m/s.

9. Potential Energy
An object can store energy as the result of its position.
Gravitational potential energy
•Gravitational potential energy is the energy stored in an object as the result
of its vertical position (i.e., height).
•The energy is stored as the result of the gravitational attraction of the Earth
for the object.
•PEgrav = mass . g . height
PEgrav = m . g . h

10. The energy is stored as the result of the gravitational attraction of the
Earth for the object.
•PEgrav = mass . g . height
PEgrav = m . g . h

11. Torque
Torque is the twisting force that tends to cause rotation. It is the measure of
how much a force acting on an object causes that object to rotate. Visit to
learn how to calculate torque along with its formula, meaning and
applications.
rF sinθ = τ torque
S.I. unit of torque: newton metre (Nm)
1.What is the difference between torque and moment?
Torque is a special case of Moment, such that it relates to the axis of the
rotation driving the rotation. Whereas moment relates to being driven b...

12. The length of a bicycle pedal arm is r = 0.152 m, and a downward
force of F = 111 N is applied by the foot. What is the magnitude of
torque about the pivot point when the angle θ between the arm &
vertical is; (a) 30.0°? (b) 90.0°? (c) 180.0°?
Ans : [8.44 Nm, 16.9 Nm, 0.00 Nm]