Sarthaks Test
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in Physics by (29.7k points)

(a) A battery lights a bulb. Describe the energy changes involved in the process. 

(b) Calculate the amount of work needed to stop a car of 500 kg, moving at a speed of 36 km/h. 

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1 Answer

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(a) Energy conversion: 

Chemical energy of battery → electrical energy → heat and light energy. 

(b) Given, 

Mass of a car, m = 500 kg, 

Speed of car, v = 36 km/h = 10 m/s 

Work needed to stop a car = K.E. of the car 


K. E. = 1 /2 mv2 

= 1 /2 × 500 × 102

= 25000 Joule

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