Acar of mass 550 kg is moving at a speed of 1.5 m/s. a man pushes the car,
increasing the speed to 3.2 m/s. how much work did the man do?
a. 2816 j
b. 3435 j
c. 2197 j
d. 4123 j

C. 2197 J

Explanation:

The work done = Energy change

The work done by man = Kinetic energy change of the car

Kinetic energy is the energy possessed by a moving object solely due to its motion.

You can get the K.E. of an object using the equation,

K.E. =  (1/2)mv²

So you get,  

The work done by man =  K.E. change of the car

                                       = (1/2)×550×(3.2)²  - (1/2)×550×(1.5)²

                                       = 2197.25 J

the correct answer is b

5 w for 1hr = 5x60x60 joules=300x60=3000x6=18,000j as total energy conversion. efficiency of bulb needed for radiant to thermal within 18000