Suppose that 6 J of work is needed to stretch a spring from its natural length of 36 cm to a length of 50 cm. (a) How much work (in J) is needed to stretch the spring from 38 cm to 46 cm?
(b) How far beyond its natural length (in cm) will a force of 45 N keep the spring stretched?

(2) (a) you have a simple circuit that consists of only a battery (δvbat=1.5v) and two resistors with resistance r1=10ω and r2=5ω, connected in series with each other. what is the current running through the battery? (b) you re-arrange your circuit so now r2 is attached in parallel to r1 rather than in series. what is the current running through the battery? (c) you add an additional resistor r3=7ω on the same branch as r2. what is the current running through the battery? (d) what is the power dissipated in r3?