Chapter 5

Exercises

1. A sharp knife cuts better than a dull knife because it has a thinner cutting area which results in more cutting pressure for a given force.

5. Both blocks have the same volume and therefore displace the same amount of water.

6. A one-kilogram block of aluminum is larger than a one-kilogram block of lead. The aluminum therefore displaces more water.

13. 0.1 or 10% above water.

15. No buoyant force act on the plug unless there is water beneath it. While in the drain there is none, once removed and placed, submerged, in the bottom of the tub there is water beneath it.

18. The water level will fall.

19. The water level will fall.

24. The water level remains unchanged.

26. While on the earth's surface our bodies push out as hard as atmospheric pressure pushes in. The higher up we go the less atmospheric there is, to compensate for this air is released through our ears.

30. At the top of a very tall mountain. There is less atmosphere to push the soda up into the straw.

34. The wood has greater mass.

37. The unpunctured balloon will move slightly down.

38. The balloon that is free to expand will rise higher up.

40. Without a wind the same pressure is pushing out to balance the inward force. A strong enough wind could produce an unbalanced force, strong enough to shatter the window.

43. The air between the car and the truck is moving faster than the air on the other side of the car. According to Bernoulli's Principle, the force on the side of the car facing the truck will be less, hence it lurches in that direction.

46. Air moves faster over the crests. Again Bernoulli's Principle states the pressure will then be less over the crests and more over the troughs.

48. This is similar to the car truck problem. The water between the ship and solid-walled wharf moves faster than the water on the other side. The ship is then drawn towards the wharf.