Sarah and her friends the swim team are playing on the high dive. one of sarah's friends throws her back pack, containing her swim supplies, into the pool from the high dive platform. the back pack weighs 50 n. when the back pack hits the water, it encounters a 50.0 n upward resistance force. the swim coach, who also happens to be the physics teacher says: "this is a great opportunity to discuss the forces exerted on sarah's back pack! "

Weight and upthrust of water on the bag are acting on the bag.

Explanation:

We all know that weight acts on the bag due to the Earth's gravitational field and it is given that the bag encounters upwards resistance force which must be in form of upthrust of water.

But as bag hit water it will not immediately come to rest although forces are balanced as it has a certain velocity as thrown from above. So the bag will sink in water amidst the resistance force where the resistance force also increase as hydro static pressure increases as depth increases. So bag will come to rest and move upwards. It will finally float on water as resistance force can balance the weight of the bag.

asthenosphere and convection