1. two charged objects repel each other when their charges are of different signs they have the same number of protons their charges are of the same signs they have the same number of electrons 2. batteries typically have two positive terminals two negative terminals one positive and one negative terminal no terminals

1. when their charges are of the same signs

Explanation:

Electrostatic force is the force exerted betwen objects that have charge. The magnitude of the force is given by:

where k is the Coulomb constant, q1 and q2 are the charges of the two objects, and r is the separation between the two objects. The sign (and therefore the direction) of the force depends on the relative signs of the two charges. In fact:

- When the two charges have same sign, the force is positive, which means that it is a repulsive force

- When the two charges have opposite sign, the force is negative, which means that it is an attractive force

So, we can conclude that

Two charged objects repel each other when their charges are of the same signs

2. Two terminals, one positive and negative

Explanation:

Batteries are devices which provides (usually through some chemical reactions) a potential difference, also called electromotive force. When connected to a closed circuit, this potential difference provided by the battery "pushes" electrons through the circuit, generating an electric current.

Batteries have generally two terminals: one terminal at positive voltage, called positive terminal, and one terminal at negative voltage, called negative terminal. When connected to the circuit, electrons are pushed from the negative terminal through the circuit towards the positive terminal of the battery.

when the velocity of a mass on a spring is zero, the acceleration is at a maximum .

find the sum of the two horizontal vectors and the sum of the two vertical vectors

isoceles right angled triangle