Asolar heated house loses about 5.4 × 107 cal through its outer surfaces on a typical 24-h winter day.

what mass of storage rock is needed to provide this amount of heat if it is brought up to initial temperature of 62°c by the solar collectors and the house is maintained at 20°c? (specific heat of rock is 0.21 cal/g⋅°c.)

a. 163 kg
b. 1 230 kg
c. 6 100 kg
d. 12 700 kg

C

Explanation:

Q=mcΔθ

Q=quantity of heat   , m= mass of the storage rock

Δθ= temperature change.

m= Q/(cΔθ)

Q=5.4

Δθ=62°C-20°C

 =42°C

c=0.21cal/g.°C

m≈6100000g

m≈6100kg

at positions a, g kinetic energy is maximum.

at position d, potential energy is maximum.

the total distance that martina travels that day is

(distance from home to mom's office) plus (distance from mom's office to school)

plus (distance from school to library) plus (distance from library to friend's house)

plus (distance from friend's house to martina's house).

(we don't know what any of these distance actually is.)