a force pushing on the object from the opposite direction a force that continually acts on the object in the direction the object is moving an increase in the mass of the object a decrease in the mass of the object
I gave my students this multiple choice question: What can cause a moving object to increase its speed in a forward direction?

Only one answer is correct among these 4 choices:
- a force pushing on the object from the opposite direction
- a force that continually acts on the object in the direction the object is moving
- an increase in the mass of the object
- a decrease in the mass of the object

Could you tell me which one is correct?

a force that continually acts on the object in the direction the object is moving