Tutor profile: Arpita S.
When an ideal gas expands into a vacuum, there is neither absorption nor evolution of heat. Why?
In an ideal gas, there are no intermolecular forces of attraction. Hence, no energy is required to overcome these forces. Moreover, when a gas expands against vacuum, work done is zero (because of Pext = 0). Hence, the internal energy of the system does not change, i.e., there is no absorption or evolution of heat.
Which of the phrases (A), (B), (C) and (D) given below should replace the phrase printed in bold in the sentence to make it grammatically correct? If the sentence is correct as it is given and no correction is required, mark (E) as the answer. "We have hired an advertising agency to prepare a campaign to encourage people votes." A. Votes by people B. People to vote C. Voting for people D. People from voting E. No correction required
B. People to vote
The force required to stretch Hooke's Law spring varies from 0 N to 65 N as we stretch the spring by moving one end 6.3 cm from its unstressed position. Find the force constant of the spring. Answer in units of N/m.
We understand from the formulation of the problem that the spring force is 65 N when the spring is stretched by x = 6.3 cm, which in SI units is x = 0.063 m. At the same time from the Hooke's law, we know that the spring force is F = kx, where is a force constant (force constant) of the spring. We substitute the known values on the above expression and obtain 65 = k * 0.063 Then k = 1032 N/m
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