Dave pushes his four-year-old son thomas across the snow on a sled. as dave pushes, thomas speeds up. which statement is true?

Unfortunately, you have not included in here the choices in which we could select our answer/s from. However, it may be noted that according to Newton's second law of motion,    
                                            F = m x a
where F is force, m is mass and a is acceleration. With the same mass, increasing the force by pushing harder, the object accelerates. Thus, increasing the speed of Thomas. 

During the 1800s. hope this !