Haley rubs a cotton cloth along a plastic strip. The plastic strip becomes positively charged. Why did this happen?

Um vetor representa um deslocamento cujo módulo é 20 m. se v faz um ângulo de 60 graus com a horizontal, qual é o valor das componentes horizontal e vertical deste vetor?

Which composition of water moves to begin a deepwater current?

Name two kinds of practical electric pumps.