posted by peter .
On a cold winter morning, a child sits on a sled resting on smooth ice. When the 9.10 kg sled is pulled with a horizontal force of 36.0 N, it begins to move with an acceleration of 2.10 m/s^2.
The 25.0 kg child accelerates too, but with a smaller acceleration than that of the sled. Thus, the child moves forward relative to the ice, but slides backward relative to the sled.
Find the acceleration of the child relative to the ice.