Table 7.1 Energy of Various Objects and Phenomena Object/phenomenon Energy in joules Big Bang 1068 Energy released in a supernova 1044 Fusion of all the hydrogen in Earth's oceans 1034 Annual world energy use 4x1020 Large fusion bomb (9 megaton) 3.8×1016 1 kg hydrogen (fusion to helium) 6.4x1014 1 kg uranium (nuclear fission) 8.0×1013 Hiroshima-size fission bomb (10 kiloton) | 4.2x1013 90,000-ton aircraft carrier at 30 knots 1.1x1010 1 barrel crude oil 5.9x10° 1 ton TNT 4.2x10° 1 gallon of gasoline 1.2x108 Daily home electricity use (developed countries) 7x107 Daily adult food intake (recommended) 1.2x107 |1000-kg car at 90 km/h 3.1x105 1 g fat (9.3 kcal) 3.9×104 ATP hydrolysis reaction 3.2x104 1 g carbohydrate (4.1 kcal) 1.7x104 1 g protein (4.1 kcal) 1.7×104 Tennis ball at 100 km/h 22 Mosquito (10- g at 0.5 m/s) 1.3x10-6 Single electron in a TV tube beam 4.0x10¬15 Energy to break one DNA strand 10-19
Kinematics
A machine is a device that accepts energy in some available form and utilizes it to do a type of work. Energy, work, or power has to be transferred from one mechanical part to another to run a machine. While the transfer of energy between two machine parts, those two parts experience a relative motion with each other. Studying such relative motions is termed kinematics.
Kinetic Energy and Work-Energy Theorem
In physics, work is the product of the net force in direction of the displacement and the magnitude of this displacement or it can also be defined as the energy transfer of an object when it is moved for a distance due to the forces acting on it in the direction of displacement and perpendicular to the displacement which is called the normal force. Energy is the capacity of any object doing work. The SI unit of work is joule and energy is Joule. This principle follows the second law of Newton's law of motion where the net force causes the acceleration of an object. The force of gravity which is downward force and the normal force acting on an object which is perpendicular to the object are equal in magnitude but opposite to the direction, so while determining the net force, these two components cancel out. The net force is the horizontal component of the force and in our explanation, we consider everything as frictionless surface since friction should also be calculated while called the work-energy component of the object. The two most basics of energy classification are potential energy and kinetic energy. There are various kinds of kinetic energy like chemical, mechanical, thermal, nuclear, electrical, radiant energy, and so on. The work is done when there is a change in energy and it mainly depends on the application of force and movement of the object. Let us say how much work is needed to lift a 5kg ball 5m high. Work is mathematically represented as Force ×Displacement. So it will be 5kg times the gravitational constant on earth and the distance moved by the object. Wnet=Fnet times Displacement.
If the energy in fusion bombs were used to supply the energy needs of the world, how many of the 9-megaton variety would be needed for a year’s supply of energy (using data from Table )? This is not as far-fetched as it may sound—there are thousands of nuclear bombs, and their energy can be trapped in underground explosions and converted to electricity, as natural geothermal energy is.
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