Introduction to Mechanical Energy

Mechanical Energy

Open Ended

What is energy?

• All bodies in the state of rest or in motion possess mechanical energy.

• Energy is the ability to do work.

• Energy is measure in joule (J).

• There are other units such as calorie (cal).

• The bigger units of energy are watt hour (Wh) and kilowatt hour (kWh).

• These bigger units are used to measure the consumption of electrical energy.
  

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What are two types of Mechanical energy?

• The energy possessed by the object in motion

​Kinetic engrgy

• The energy possesses by the object at rest

​Potential energy

Mechanical Energy

• Velocity of object

• mass of the object

​Kinetic energy

• Gravity

• height of object placed

• mass of the object

​Potential energy

Factors affecting mechanial energy

• KE = ½mass x Velocity²

​Kinetic energy (KE)

• PE ∝ to mass (m)

• PE ∝ height (h)

• PE ∝ gravity (g)

• Therefore,

• PE= mass x gravity x height

​Potential energy (PE)

Formula of mechanical energy

Exercises

1. What is the kinetic energy of the object having a mass of 4 kg thrown with a velocity of 15 m/s?

3. Calculate the potential energy of a box of weight 20 kg placed on top of a cupboard of height 2m.

2. A car of mass 1000 kg is moving with a velocity of 20 m/s. What is the kinetic energy of the car? What will happen to its kinetic energy if its mass is doubled?