Acertain radar installation tracks airplanes by transmitting electromagnetic radiation of wavelength 4.0 cm.
a)find the frequency of this radiation. b)find the time required for a pulse of radar waves to reach an airplane 4.8 km away and return.

a) frequency =

b) times =

Explanation:

Part a)

As we know that frequency of radiation is given as

now we know that

now frequency is given as

Part b)

Time required for the pulse to reach the airplane and return is given by formula

total distance for moving to and fro = 4.8 km + 4.8 km = 9.6 km

speed of the wave =

now times is given as

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note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.