• An object is said to be in motion if it changes its position with respect to its surroundings in a given time.
• An object is said to be at rest if it does not change its position with respect to its surroundings.
• A frame of reference is another object or scene with respect to which we compare an object'* position
Look at the figures. In figure1, the car is to the right of the tree. In figure 2, after 2 seconds, the car is to the left of the tree. As the tree does not move, the car must have moved from one place to another. Therefore, here the tree is considered as the frame of reference.
