Answer:
A light emitting diode (a semiconductor diode which glows when voltage is applied.
Answer : Option B) Perfect Circles
Explanation : In heliocentric model where sun is considered to be the center and earth and other planets revolves around it. The shape of the objects in the space is perfectly circle as they move around the sun.
Options (b) and (d) are correct about an electric motor.
An electric motor is a device which coverts electrical energy into mechanical energy.It works on the principle that when a current carrying coil is placed in a magnetic field, it experiences torque. Because of that torque, the coil rotates and thus the electrical energy gets converted into mechanical (motion) energy.
Using KE = 1/2mv^2
m = mass (80kg)
v = velocity (?)
KE = kinetic energy (2500J)
2500/((1/2) x (80)) = v^2
Square root the answer to get: 7.91 m/s
