Question

What type of energy is stored in the spring of a watch?
A.Potential energy
B.Kinetic energy
C.Heat energy
D.Elastic potential energy

Answer 1

The spring-based watches are driven by a mainspring. A mainspring is a spiral torsion spring of metal ribbon. When the key or knob is turned energy gets stored in the main spring by twisting the spiral tighter. This energy is then used to turn the watch hands.

Complete answer:
Potential energy of any object is the energy by virtue of its position, arrangement or state of the object. This energy is stored in an object. There are mainly two types of potential energy namely gravitational and elastic potential energy.
Kinetic energy of any object is the energy due to its motion. It is defined as work needed to accelerate a body from its state of rest to its stated velocity. The kinetic energy depends only on the square of speed of the object unless the object is moving with a much higher speed. i.e. speed comparable to that of light.
Heat is the amount of energy in transit as a result of temperature difference. When you touch a cup of tea you feel hot this happens because the temperature of the cup is higher than your body temperature. Similarly you feel cold when the body you are in contact with has temperature lower than that of yours.
Elastic potential energy is a kind of potential energy stored as a result of deformation of an elastic object, such as stretching or compressing of rubber bands, springs and bungee cords. The more an object is stretched, more is its elastic potential energy.
In a spring based watch, mainspring powers the watch. Mainspring is a spiral ribbon of spring steel. It is inside a cylindrical barrel with the outer end of mainspring attached to the barrel. When we turn the knob to wind the timepiece, energy gets stored in the mainspring. Barrel is then turned by the force of mainspring. The barrel uses gear teeth to move the watch hands.
Now we can conclude that the energy stored in spring of a watch is elastic potential energy.

Therefore, option D is correct.

Note:
To understand the type of energy stored in the spring watch we must understand the mechanism of spring watch. The spring-based watches contain a mainspring which stores elastic potential energy on winding the timepiece. This energy is then utilized to rotate the watch hands.