4.a 10- kg mass is attached to a spring, stretching it 0.7 m from its natural length. the mass is started in motion from the equilibrium position with an initial velocity of 1 m/s in the downward direction. a. find the equation of motion assuming no air resistance. b.when is the first time the mass goes through the equilibrium position after it was set in motion. c. find the equation of motion assuming air resistance equal to -90x’(t) newtons. d.what is the long term behavior of the motion described in part (c)?

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.

The human body stores chemical energy from digested food. some of the chemical energy is converted into mechanical energy when the body moves. which statement best supported by this information

Asmall 12.00g plastic ball is suspended by a string in a uniform, horizontal electric field with a magnitude of 10^3 n/c. if the ball is in equilibrium when the string makes a 30 ° angle with the vertical, what is the net charge on the ball?