Answer:B
Explanation:
Given
speed of car 
mass of clump 
Radius of car tire 
Since the tire is rotating about axle so a centripetal force is acting constantly on each particle towards the center of tire.
Centripetal force is given by
where 
(inward)
Efficiency = (energy that does the job) / (total energy used)
= (45 J) / (120J)
I think you can handle the division.
Answer:
1.84 kJ (kilojoules)
Explanation:
A specific heat of 0.46 J/g Cº means that it takes 0.46 Joules of energy to raise the temperature of 1 gram of iron by 1 Cº.
If we want to heat 50 g of iron from 20° C to 100° C, we can make the following calculation:
Heat = (specific heat)*(mass)*(temp change)
Heat = (0.46 J/g Cº)*(50g)*(100° C - 20° C)
[Note how the units cancel to yield just Joules]
Heat = 1840 Joules, or 1.84 kJ
[Note that the number is positive: Energy is added to the system. If we used cold iron to cool 50g of 100° C water, the temperature change would be (Final - Initial) or (20° C - 100° C). The number is -1.84 kJ: the negative means heat was removed from the system (the iron).
