### Overarch 2

Bricks are 20cm long and 10cm high. How high could an arch be built without mortar on a flat horizontal surface, to overhang by 1 metre? How big an overhang is it possible to make like this?

### Stonehenge

Explain why, when moving heavy objects on rollers, the object moves twice as fast as the rollers. Try a similar experiment yourself.

### Maximum Flow

Given the graph of a supply network and the maximum capacity for flow in each section find the maximum flow across the network.

# A Circuit Problem

##### Age 16 to 18 Short Challenge Level:

In the circuit shown below, find the current labelled $I_x$ when V = 14 V.

Extensions:

If mesh current analysis is used to to solve this problem, how many unknown currents are there in the circuit? How many simultaneous equations will you end up with?

If nodal voltage analysis is used to solve the problem, what is the minimum number of unknown voltages that would need to be added to the diagram?

Can you think of any ways in which the central branch of the circuit could be simplified without affecting the current $I_x$?

Could you solve this problem using Thevenin and Norton's theorems?