Answer and Explanation:
The main source of earth magnetic field is the metals and iron present in earth crust these metals are mainly found in liquid state in earth crust and we know that whenever there is spinning of these liquid metals then there will magnetic field generate, So the main source of earth magnetic field is the metals present in earth crust.
The mechanical efficiency = actual work / ideal work
So ζ = 1540 / 1600 * 100% = 96.25%
Answer: Yes
Explanation:
Velocity
is defined as the distance traveled
in a specific time
:

If you are traveling at
a distance
, then the time it will take you to be at work is:


This means you will make it on time, because this time is less than 0.25 h.
C. meter per second
Velocity and speed share the same SI unit.
Answer:
astronauts age is 32 years
correct option is e 32 years
Explanation:
given data
travels = 20 light year
stay = 2 year
return = 52 years
to find out
astronauts aged
solution
we know here they stay 2 year so time taken in traveling is
time in traveling = ( 52 -2 ) = 50 year
so it mean 25 year in going and 25 years in return
and distance is given 20 light year
so speed will be
speed = distance / time
speed = 20 / 25 = 0.8 light year
so time is
time = 
time = 
time = 15 year
so age is 15 + 2 + 15
so astronauts age is 32 years
so correct option is e 32 years