Two point-like charged objects are released at rest in otherwise empty space. As time goes on, the magnitude of the electrostatic force exerted on each of the objects decreases. Which of the following must be true?
(A) Both particles are negatively charged
(B) Not enough info
(C) The particles may be either both positively charged or both negatively charged
(D) One particle is positively charged and the other is negatively charged
(E) Both particles are positively charged

Asun-sized star will spend most of its lifetime as a: white dwarf red giant protostar main-sequence star

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 710 n/m. it is initially at rest on an inclined plane that is at an angle of θ = 23° with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is μk = 0.19. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. a) what is the block's initial mechanical energy? b) if the spring pushes the block up the incline, what distance, l, in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.

Awheel of mass 48 kg is lifted to a height of 0.8 m. how much gravitational potential energy is added to the wheel? acceleration due to gravity is g = 9.8 m/s2. a. 30.4 j b. 3.1 j c. 297.9 j d. 11,321 j