Question

Problem 10: Suppose a battery operates a 1.95 W electric clock for 16 months. A) What is the available energy content, in joules, of the battery? B) How many years can a battery that supplies 7.75 X 10' J run a pocket calculator that consumes energy at the rate of 0.95 x 10-3 W? Problem 4: Consider the kinetic energy of a 22000-kg truck moving at 107.5 kmh and that of an 92.5- kg astronaut in orbit moving at 27500 km/h. A) What is the ratio of the kinetic energy of the truck to the kinetic energy of the astronaut?

Answer 1

Problem 10

A) Energy = Power x time = 1.95 W x 16x30x24x3600s = 80870400 Joules

B) t = Energy/Power = 77500/0.00095 = 81578947 seconds = 2.586 years

Problem 4

Kinetic energy = 1/2 mv^2

107.5 km/h = 29.861 m/s

27500 km/h = 7638.9 m/s

Ratio = (22000 x 29.861²)/(92.5 x7638.9²) = 0.0036344