Ch 20: The First Law of ThermodynamicsSee all chapters
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Ch 01: Units & Vectors
Ch 02: 1D Motion (Kinematics)
Ch 03: 2D Motion (Projectile Motion)
Ch 04: Intro to Forces (Dynamics)
Ch 05: Friction, Inclines, Systems
Ch 06: Centripetal Forces & Gravitation
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Ch 20: The First Law of Thermodynamics
Ch 21: The Second Law of Thermodynamics
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Ch 38: Quantum Mechanics

First Law of Thermodynamics

See all sections
Sections
Internal Energy
Introduction to Heat Capacity
First Law of Thermodynamics
Intro to Thermal Processes
Work & PV Diagrams

Concept #1: Changes in Internal Energy

Concept #2: The First Law of Thermodynamics

Practice: 2.5 moles of an atomic hydrogen gas are stored in a cylinder with a moveable piston, sitting in a bucket of ice. The piston is moved SLOWLY, decreasing the volume from 0.03 m3 to 0.01 m3 . How much ice melts during this movement? Work done at constant pressure is given by 𝑊 = −𝑃Δ𝑉, and work done at constant temperature by 𝑊 = −𝑛𝑅𝑇𝑙𝑛 ( 𝑉𝑓/𝑉𝑖 ). Note that the latent heat of fusion for water is 334 kJ/kg.

Additional Problems
An athlete doing push-ups performs 650 kJ of work and loses 425 kJ of heat. What is the change in the internal energy of the athlete? a) -225 KJ b) -1075 KJ c) 1075 KJ d) 225 KJ  
A skater pushes straight away from a wall. She pushes on the wall with a force whose magnitude is F, so the wall pushes on her with a force F (in the direction of her motion). As she moves away from the wall, her center of mass moves a distance d. Consider the following statements regarding energy. I ΔKtrans + ΔEinternal = Fd II. ΔKtrans + ΔEinternal = −Fd III. ΔKtrans + ΔEinternal = 0 IV. ΔKtrans = Fd V. ΔKtrans = −Fd What is the correct form of the energy principle for the skater as a real system and as a point particle (PP) system? 1. Real: II, PP: V 2. Real: I, PP: V 3. Real: II, PP: IV 4. Real: V, PP: I 5. Real: IV, PP: III 6. Real: III, PP: IV 7. Real: V, PP: IV 8. Real: I, PP: IV 9. Real: III, PP: V 10. Real: IV, PP: IV
Consider the head-on collision of two masses, m1 = 3 kg moving to the right with speed 6 m/s and m2 = 6 kg moving to the left with speed 3 m/s. Given that they stick together after the collision, what is the increase in internal energy of the system during the collision? Assume no energy is lost to the surroundings and neglect any external forces acting on the two masses. 1. 81.0 J 2. 56.25 J 3. 40.5 J 4. 216.0 J 5. 303.75 J 6. 112.5 J 7. 144.0 J 8. 375.0 J 9. 525.0 J 10. 72.0 J
Six moles of a monatomic ideal gas undergo the process shown in the figure. State 1 has pressure p1 = 4.00 x 105 Pa and volume V1 = 2.00 x 10-3 m3. State 2 has pressure p2 = 3.00 x 105 Pa and volume V2 = 6.00 x 10-3 m3.  a) In this process, what is ΔU, the change in the internal energy of the gas? b) What is the heat flow Q for this process?  c) Does heat flow into the gas or out of the gas?      
The temperature of 5.0 moles of an ideal gas is increased from 100°C to 300°C. If this is done at constant volume, 3.0 x 104 J of heat energy flows into the gas. If the same temperature change is carried out at constant pressure, the heat flow into the gas is (a) 3.0 x 104 J (b) less than 3.0 x 104 J (c) greater than 3.0 x 104 J