Questions 11-13 refer to the image below.    Salvador Dali, Persistence of Memory, 1931 11.  The above painting is an example of which of the following developments during the early twentieth century?

A spring stretches 20 cm when a force of 30 N pulls on it. The spring constant for this spring is closest to

A white dwarf can exhibit an astonishing density of ρ ≈ 1000 kg/cm3.  If one had material from a white dwarf that was contained within a paintball of diameter D ≈ 1.8 cm, what would be its mass in kg?   Insert those values directly into the formula: M ≈ ρ x D3 / 2 , and in this instance, provide the answer without units and rounded to the nearest integer (e.g., 80.6 -> 81). 

The extra practice questions don’t count toward a student’s grade. 

Wire 2 is twice the length and has twice the cross-sectional area that of wire 1. What is the ratio R2/R1 of their resistances?

What is the resistance of 1.0 m of a solid cylindrical metal cable having a diameter of 0.40 inches and a resistivity of 1.68 × 10-8 Ω ∙ m?

Compared to the free market, the change in producer surplus from this policy equals

A rational decision maker takes an action only if

Suppose that instead of a tax, government imposes a subsidy of $4. What is the consumer surplus?

Suppose that instead of a price floor, there is a price ceiling equal to $6. Consumer surplus equals