Final answer:
Letting a friend ride on your sled increases the mass, and according to Newton's second law of motion, if the force remains the same, the acceleration would decrease. The more mass there is, the less acceleration will occur for the same amount of force.
Step-by-step explanation:
If you let a friend ride with you on your sled, thereby increasing the mass, the acceleration would decrease. This scenario is described by Newton's second law of motion, which can be stated as F = ma, where F is the net force applied to an object, m is the mass of the object, and a is the acceleration of the object. When the mass increases but the applied force remains constant, the acceleration must decrease to balance the equation.
For example, if you are riding solo on the sled and experiencing acceleration, this indicates that a net force is acting upon you and your sled's mass. But if a friend joins you, this increases the total mass, and unless the net force also increases, the same force spread over a larger mass yields smaller acceleration. Hence, the correct answer is C. Yes, the acceleration would decrease.