# Need help Physics As level OCR

A small block of wood is placed in deep water.
The block is at rest with 80% of its volume under the surface of water. The weight of the block is 6.0 N.
What is the upthrust acting on the block?
A0
B 1.2 N
C 4.8 N
D 6.0 N

I don’t understand why the answer is D(6.0N)

Thanks
When the block is at rest, the net force acting on the block is zero (Newton's First Law). Since the block is not moving, no drag force acts on the block. So the only two forces which act on the block is its weight (downwards) and upthrust (upwards). As net force is zero, upthrust=weight. Therefore, Upthrust= 6.0 N, since weight is 6.0 N as given in the question statement.

Hope it helps!
Original post by NBH09
When the block is at rest, the net force acting on the block is zero (Newton's First Law). Since the block is not moving, no drag force acts on the block. So the only two forces which act on the block is its weight (downwards) and upthrust (upwards). As net force is zero, upthrust=weight. Therefore, Upthrust= 6.0 N, since weight is 6.0 N as given in the question statement.

Hope it helps!

Appreciate,great help