Which is an example of gaining a static charge by conduction? a) rubbing a balloon against your hair. b) shuffling your shoes across a carpet. c) bringing a charged rod near an electroscope. d) touching your car on a cold day and getting a shock.

 D) Touching your car on a cold day and getting a shock.

Explanation:

Ok, there are 3 forms of generating static charge:

Friction: This is one of the most common examples, the static charge is generated as you rub an object with another, and in the process, one of the objects "steals" electrons of the other object, and in this way generates a static charge. Examples of this are option A and B.

Induction: You have a charged object, and you put it near another object that may steal electrons. In this way you are "inducing" statical charge in the other object; an example of this is option C.

Conduction: In this case, you "connect" two objects and thanks to this connector, electrons of one object (the most charged one) can flow to the other. For example, in option D "Touching your car on a cold day and getting a shock." the car and you are the objects, and when you touch the car, your finger is the connector between you and the car that allows the conduction to happen.

coil wire, increase current, put iron inside the coil

can be answered using momentum.

momentum = p

p1= mass1 * velocity1

p1 = p2

therefore

p1 = 6kg * 4m/s

p1 = 24kgm/s

p2=m2 * v2

24 kgm/s = 7kg * v2

v2 = 24 kgm/s / 7kg

v2= 3.42 m/s