Which of the following causes your hands to feel warm when you rub them together?
~normal force
~spring force
~gravity
~friction

Friction

Explanation:

Hi there! I'm glad I was able to help you!

Friction would be your best option.

I chose friction as the answer after using the process of elimination.

Normal force, in a simple definition, is basically when nothing happens and an object is sitting on top of another, so the net force is zero. In our case, we're rubbing our hands together, so option A is out of the question.

Spring force, which is much different than normal force, requires the use of an actual spring. It's a force that compresses AND decompresses a spring.

Gravity is the force that keeps us (and other objects), from floating into the air. Gravity is like a giant human magnet!

Finally, the force of friction acts in the complete and total opposite direction of the way an object, any object (in this case, our hands), want to slide. When we rub our hands together, it kind of activates the molecules and stuff inside of them to turn on, or activate, just a little bit quicker than before your hands even touched together. The faster the molecules move, the higher the temperature becomes!

I hope this helped you! Comment below if you have any other questions! :)

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.