It's not so much a "contradiction" as an approximation. Newton's law of gravitation is an inverse square law whose range is large. It keeps people on the ground, and it keeps satellites in orbit and that's some thousands of km. The force on someone on the ground - their weight - is probably a lot larger than the centripetal force keeping a satellite in orbit (though I've not actually done a calculation to totally verify this). The distance a falling body - a coin, say - travels is very small, and over such a small distance gravity is assumed/approximated to be constant.
Answer:
B
This is because frictional energy is similar to thermal energy in a system. Therefore the thermal energy produced is equal to
Answer: Magnitude of electric field = 6.77×10^11N/C
Explanation: Electric field= E =KQ/ r ^2
Given:
Total charge Q=53.2nc
Radius 84cm= 0.84m
Coulombs constant K= 8.987x10^9NmC^-1
E =(( 8.987×10^9) × 53.2) /(0.84^2)
E = ( 4 . 777 ×10 ^ 9 )/ 0.7056
E = 6.77 × 10^ 11 NC^-1
The answer is D.
C and A are incomplete as they only treat specific types of energy, and B doesn't answer the question.