How far should an object be held from a concave mirror of focal length 40cm so as to obtain a real image twice the size of the object? 1. 10cm
2. 20cm
3. 30cm
4. 60cm

An inclined plane wrapped around a metal shaft is a a. lever b. screw c. pulley d. wedge

The energy equivalent of the rest mass of an electron is

The field lines around one end of a bar magnet are shown below based on the diagram, what can you conclude about the pole of the magnet? a.is a south pole because the field hnes spread out from this end b.a north pole because the field lines spread out from this end c.a nouth pole because the field lines enter the magnet at this end d.is a north pole because the field lines enter the magnet at this end