Suppose that 2j of work is needed to stretch a spring from its natural length of 30cm to a length of 42cm
how much work is needed to stretch the spring from 35 to 40cm

so hookies law
work = kx^(2)

i get

k = 2/144

The first-order reaction a→2b+c has rate constant 0.538 s−1. if the initial concentration of a is 0.867 mol l−1, what is the half-life of the reaction in seconds? remember to use correct significant figures in your answer (round your answer to the nearest hundredth). do not include units in your response.