Explanation:
i guess using a ruler.so first on the opposite side use your eye to alighn the ruler to the light from Ray box then draw a line or you can use pins and place them alighned to the Ray box an draw a line connecting the pins
Gravitational force of attraction between two objects can be calculated from the following formula:

Where m with subscript stands for mass of the object and r is the distance between them.
When we double the mass of those two objects, distance between them stays the same, while in the numerator we have:

When numerator in the second case 4 times greater than the 'original' numerator and denominator stays the same, force becomes 4 times greater.
Remark
There are 2 kinds of Beta Decay. This one is an example of a neutron becomes a proton and the emitted particle is an electron.

Answer:
an open circuit (A battery, bulb, wire,switch)
Explanation:
the battery supplies the power the wire carries the current from the battery to the bulb but the circuit is not completed if the switch is not connected (Switch )
The current will be 2 Ampere because voltage is directly proportional to the current.