Um bloco de massa 3,0 kg é abandonado com velocidade inicial nula no ponto A de um plano inclinado com atrito, como mostra a figura. O bloco atinge o ponto B com uma velocidade de 10 m/s. Supondo que a força de atrito exercida pelo plano inclinado sobre o bloco tenha sido constante e que , calcule: a) o módulo da aceleração do bloco durante a descida;
b) o módulo da força de atrito exercida sobre o bloco;
c) o módulo da força exercida pelo plano inclinado sobre o bloco.
Considere .

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?