The lid of a jar of preserves has a radius of 3.5 cm. To unscrew the lid requires a couple of 15 Nm.
a. a If the lid is to be opened by hand, calculate the minimum force that must be applied to each side of the lid if it is to turn.
b. b A kitchen gadget, with 15-cm-long handles, can clamp onto the lid. Calculate the minimum force that must be applied to the gadget's handles to unscrew the lid.
c. c Suggest why consumers are happy to buy such a gadget rather than just use their hands.