A rightward force of 20.0 N is applied to a 4.0-kg object to accelerate it to the right across a rough surface. The object accelerates at 2.0 m/s/s. How much friction does the object experience

1. do the particles in the medium material move in the same direction of the wave or at opposite direction to the wave? explain your answer. 2. by inputting more energy into the wave, i.e a large shake of the spring, which wave property also increases? 3. are there forces of friction acting while a wave is passing through a medium?