Two points on a velocity-time graph have coordinates (2s, 5m/s) and (4s, 15m/s). Calculate the mean acceleration

An air force jet flying with a speed of 335m/s went past an anti-aircraft gun. How far is the aircraft 5s later when the gun was fired?

In the diagram above, the galvanometer is converted to 

The diaphragm in the camera is similar to what part of the eyes?

The device for measuring the angle of dip is