1. A cable that weighs 10 N/m is used to bring up 60 N of ore from the bottom of a shaft 120 meters below.

(i) Suppose that at some point x meters of cable have been brought to the surface. Then the work to go up x meters more is about w(x)x . What is w(x)? w(x)=

Express your answer with a formula.

(ii) What, in Joules, is the work required to bring the ore to the surface? Round the answer to 3 significant digits. Answer: Joules

2. The natural length of a spring is 10 cm and a force of 15 N must be exerted to lengthen it to 20 cm.

(i) Determine, in Newtons, the force F(x) required to stretch the spring x meters (relative to its position at rest). Watch out for units! F(x)=

(ii) Determine, in Joules, the work required to lengthen the spring from 10 cm to 20 cm. Watch out for units! Responnse:

(iii) Determine, in Joules, the work required to lengthen the spring from 20 cm to 30 cm. Watch out for units! Answer: