What causes a object to slow down when no longer being pushed?

Place me with this question is my last question

Each neuron shown in this figure innervates a group of muscle fibers. what is the term for a group of muscle fibers innervated by a single neuron?

It is necessary to determine the specific heat of an unknown object. the mass of the object is 201.0g it is determined experimentally that it takes 15j to raise the temperature 10°c. what is the specific heat of the object? 3,020,000 j/kg ∙ k 1500 j/kg ∙ k 0.00130 j/kg ∙ k 7.46 j/kg ∙ k