Work And Energy
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Work and Energy Work -the product of force and distance the object moves under the influence of that force and in the direction of the force -a scalar quantity
Energy -the ability to do work -expressed in joules or ergs -it is a scalar quantity
Different Scientist Gaspard Coriolis -he called the product of force and displacement the object moves under the influence of that force as work.
James Watt -he had originated another unit power to sell his improved steam engine. -he compared the rates at which work could be done by his engine and by a horse, he called this unit as horsepower.
Power • the rate of doing work • the SI unit of power is watt (W), named after James Watt who improved the steam engine • kilowatt-hour abbreviated as kwh is not a unit of energy being a product of power (kilowatt) and time (hour) • another unit of power is the horsepower, abbreviated as hp • this unit is commonly used to rate motors and engines • 1 hp= 746 watts
Formulas Work >W= Fd
Potential Energy >P.E.= mgh
Elastic Potential Energy >P.E.= 1/2 kx²
Kinetic Energy >K.e.= 1/2 mv² Work-Energy Theorem >W=Fdx
Conservation of Mechanical Energy >EM=P.E + K.e. = constant
Power >P=W/t = Fd/t
Solve Problem Energy A 75.0 kg child climbs a 6.00 m long slide that is inclined 30.0° with the horizontal. What is the potential energy of the child with respect to the ground ? SOlution Given m= 75.0 kg h= 6.00m sin 30.0° L= 6.00 m Ð= 30° p.e= ? p.e.= mgh p.e. = (75.0 kg) (9.8m/s) (3.00m) p.e. = 2 205j = 2210j
exercise • A 30 kg child enters the final section of a waterslide travelling at 2.0 m/s. The final section is 5.0 m long and has a vertical drop of 3.0 m. The force of friction opposing the child's motion is 50 N. Find a) the loss of potential energy, b) the work done by friction in the final section and c) the child's velocity at the end of the section (using energy considerations). • a) A 2000 kg car is travelling 50 miles per hour. Find the kinetic energy in Joules. b) The same car is lifted vertically upward and then dropped from rest. Find the height from which it is dropped if it strikes the ground at 50 miles per hour (neglect air resistance).
References • Physics book (chapter 6. pp. 114-125) • http://theory.uwinnipeg.ca/physics/work/node12.h tml#SECTION00580000000000000000
Energy -the ability to do work -expressed in joules or ergs -it is a scalar quantity
Different Scientist Gaspard Coriolis -he called the product of force and displacement the object moves under the influence of that force as work.
James Watt -he had originated another unit power to sell his improved steam engine. -he compared the rates at which work could be done by his engine and by a horse, he called this unit as horsepower.
Power • the rate of doing work • the SI unit of power is watt (W), named after James Watt who improved the steam engine • kilowatt-hour abbreviated as kwh is not a unit of energy being a product of power (kilowatt) and time (hour) • another unit of power is the horsepower, abbreviated as hp • this unit is commonly used to rate motors and engines • 1 hp= 746 watts
Formulas Work >W= Fd
Potential Energy >P.E.= mgh
Elastic Potential Energy >P.E.= 1/2 kx²
Kinetic Energy >K.e.= 1/2 mv² Work-Energy Theorem >W=Fdx
Conservation of Mechanical Energy >EM=P.E + K.e. = constant
Power >P=W/t = Fd/t
Solve Problem Energy A 75.0 kg child climbs a 6.00 m long slide that is inclined 30.0° with the horizontal. What is the potential energy of the child with respect to the ground ? SOlution Given m= 75.0 kg h= 6.00m sin 30.0° L= 6.00 m Ð= 30° p.e= ? p.e.= mgh p.e. = (75.0 kg) (9.8m/s) (3.00m) p.e. = 2 205j = 2210j
exercise • A 30 kg child enters the final section of a waterslide travelling at 2.0 m/s. The final section is 5.0 m long and has a vertical drop of 3.0 m. The force of friction opposing the child's motion is 50 N. Find a) the loss of potential energy, b) the work done by friction in the final section and c) the child's velocity at the end of the section (using energy considerations). • a) A 2000 kg car is travelling 50 miles per hour. Find the kinetic energy in Joules. b) The same car is lifted vertically upward and then dropped from rest. Find the height from which it is dropped if it strikes the ground at 50 miles per hour (neglect air resistance).
References • Physics book (chapter 6. pp. 114-125) • http://theory.uwinnipeg.ca/physics/work/node12.h tml#SECTION00580000000000000000
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