How is an electromagnet different from a bar magnet?
question 3 options:
a. only a bar magnet has a magnetic field.
b. only an electromagnet attracts materials made of iron.
c. an electromagnet is temporary and is magnetic when a current flows through a wire wrapped around the core.
d. a bar magnet is a temporary and is only magnetic when a current flows through a wire wrapped around the core.

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 740 n/m. it is initially at rest on an inclined plane that is at an angle of theta= 26 with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is uk = 0.17. 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. the block's initial mechanical energy is 9.472 j.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.