What is the change in potential energy of the block spring earth system between figure 1 and figure 2

Truck traveling west on the highway experiences an acceleration to the east. what could be the cause of this acceleration

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

Point charges q1 = 51 µc and q2 = −27 µc are placed 1.0 m apart, with q2 on the right. what is the force (in n) on a third charge q3 = 19 µc placed midway between q1 and q2? (assume the positive direction is to the right. indicate the direction with the sign of your answer.)