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### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

Book edition 4th
Author(s) Randall D. Knight
Pages 1240 pages
ISBN 9780133942651

# A communications truck with a 44-cm-diameter dish receiver on the roof starts out 10 km from its base station. It drives directly away from the base station at 50 km/h for 1.0 h, keeping the receiver pointed at the base station. The base station antenna broadcasts continuously with 2.5 kW of power, radiated uniformly in all directions. How much electromagnetic energy does the truck’s dish receive during that 1.0 h?

0.000181J

See the step by step solution

## Given Parameters

radius of dish(r): 44/2 cm= 0.22m

v = 50km/h = 50000m/h = 13.88m/s

Time = 1hr

## Concept

Energy received by dish is power received over the course of 1hr time period.

____ eq (1)

Now, Intensity received by dish is ,

Where, P = power

A = Area

So, P = IA

## Substituting this in eq(1) we get____ eq(2)Now intensity received by dish = =Putting this in eq(2) we get;

____ eq(3)

Now we know that the truck is moving away from the station at a constant speed. So truck's distance from station at any time t is

Substituting this in equation 3 we get,

Here A =

Substituting this value in above equation we get: