average velocity is vector displacement / time
time is "almost exactly one hour"
disp = -10m
v= -10/1x60x60 = -1/360m/s
Answer: 58.8235 km/h
speed = distance/time
the distance is 10 km
the time is 10 minutes
the unit is not correct, so we first change minute to hour
so 10/60 is 0.166667, rounded to 0.17.
10 km/ 0.17 hours =
The answer is B. Unbalanced force
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).
