Give three forces that can make an object change shape.

I am not sure if this question is asking about force and physics or if this question is leaning more toward physical forces that change the shape of Earth's surface.  By definition, a force is either a push or a pull.  I could list out many different pushes or pulls to give three things that change shape, but I do not think that is what the question is asking.  I think the question is asking for three forces that can change the shape of Earth's features.  

Weathering and erosion—As surface features like rocks are weathered away through physical or chemical forces, the feature changes shape.  It becomes rounder, more sloped, or something else.  This is how canyons are made and how mountains are weathered down.  Materials are eroded, carried somewhere else, and then deposited in a new location which changes the shape of that general area as well.  

Compression forces at plate boundaries—This can cause breaks in the crust called faults.  Because the fault line is pressing together, reverse faults are created.  This kind of plate movement can also build mountains as the crust buckles upward.  This is what is happening at the plate boundary of India and Asia.  The Himalayas are still being pushed upward because of these forces. 

Magma movement—As magma makes it way to the surface of Earth, it pushes the ground up.  Even before a volcano erupts, scientists are able to track the shape changes in the mountain.  The mountain could get steeper, it could develop a bulge on one side, and so on.  After an explosive eruption, the mountain might not even exist anymore.  This is what happened with Krakatoa in the late 1800s.   
https://www.physicsclassroom.com/class/newtlaws/Lesson-2/The-Meaning-of-Force