Question

2) Suppose a woman does 550 J of work and dissipates 9800 J of heat in the process.

(a) What is the decrease in her internal energy, assuming no change in temperature or consumption of food? (That is, there is no other energy transfer.) Express your answer in kcal.
kcal
(b) What is her efficiency?
%

3) (a) How long will the energy in a 310 kcal cup of yogurt last in a woman doing work at the rate of 160 W with an efficiency of 20.0% (such as in leisurely climbing stairs)?
min

(b) Does the time found in part (a) imply that it is easy to consume more food calories than you can reasonably expect to work off with exercise?

No Yes

4) A granite column in a building is 9.00 m high and has a mass of 2.16 ✕ 10⁴ kg.

(a) How much heat is needed to increase its temperature by 10.5°C, given its specific heat is 0.200 kcal/kg·°C?
J
(b) What is its change in length if its coefficient of linear expansion is 2.50 ✕ 10^-6/°C?
m
(c) Calculate the force it would exert if not allowed to expand, given its cross-sectional area to be 1.00 m² and the Young's modulus for granite to be 45.0 ✕ 10⁹ N/m². Note that this force is much larger than the weight it supports, so that it will expand almost freely.
N
(d) How much work does it perform when it expands, if it supports a mass of 1.00 ✕ 10⁴ kg?
J
(e) What is its change in internal energy?
J

5) A hand-driven tire pump has a 3.00 cm diameter piston and a maximum stroke of 31.0 cm.

(a) How much work do you do in one stroke if the average gauge pressure is 2.40 ✕ 10⁵ N/m² (about 35 psi)? (You may consider this an isothermal process.)
J
(b) What average force do you exert on the piston, neglecting friction and gravity?
N

Answer 1