Final answer:
The physical weathering of rock by the repeated thawing of water, also known as frost wedging, is likely to happen more quickly than the physical weathering of rock by plant roots, due to the rapid expansion and contraction of water as it freezes and thaws.
Step-by-step explanation:
When considering the processes of physical weathering of rock, it is noted that different mechanisms have varying rates of effectiveness. The weathering of rock by plant roots occurs as the roots grow into cracks and fissures in the rock, gradually prying the rock apart. This process is generally slow since it is dependent on the growth rate of the plants and their roots.
On the other hand, the physical weathering of rock by the repeated thawing of water, also known as frost wedging, is a more rapid process. Water that seeps into cracks in rock and subsequently freezes will expand, exerting pressure on the rock and causing it to crack and break apart. This cycle of freezing and thawing can occur multiple times within a single season, leading to a quicker disintegration of the rock compared to the gradual growth of plant roots.