Answer to Question #326266 in Mechanics | Relativity for Anonymous005

Question

a) A driver was speeding with 40 m/s in his 1800 kg car when he notices a police car with a radar and slows down to a legal speed of 19 m/s. What is the change of the kinetic energy of the car? What is the amount of work done on the car during the deceleration?

b) A repairman of mass 80 kg climbed a 10 m vertical latter to reach the roof of a building in 12 seconds. What is the power developed by the man against gravity?

Answer 1

a)

$∆E=\frac m2(v_2^2-v_1^2)=-1.12~MJ,$

$A=-∆E=1.12~MJ.$

b)

$P=\frac{mgh}t=654~W.$