C6problems

# C6problems - Chapter 6 Problems 1. How much pressure do you...

This preview shows pages 1–3. Sign up to view the full content.

Chapter 6 Problems 1. How much pressure do you experience when you balance a 5-kg ball on the tip of your finger, which, let us say, has an area of 1 cm 2 ? Pressure is force/area. The force of gravity on the ball is mg = 5 x 10 = 50 N. Convert 1 square cm to square meters. There are 100 cm in a meter or 10,000 square cm in one square meter. So, 1 cm 2 = 10 -4 m 2 . So P = 50 / 10 -4 = 5 x 10 5 Pa or about 5 times atmospheric air pressure. 2. A 6-kg piece of metal displaces 1 liter of water 2h3n wugm34t3e. What is its density? Density is just mass/volume. Convert 1 liter into cubic meters. 1 liter = 10 -3 m 3 . So, density of metal = 6 kg / 10 -3 m 3 = 6000 kg/m 3 . 3. The depth of water behind the Hoover Dam in Nevada ais 220 m. What is the water pressure at the base of this dam? (ignore the pressure due to the atmosphere.) Pressure is just the weight of the water above a unit area. So, we need the weight of a column of water that is 1 m 2 at the base and 220 m tall. The volume of this water is 220 m 3 . The density of water is 10 3 kg/m 3 . So the total mass of water is 220,000 kg. The weight of the water is mg or 2.2 x 10 6 N. So, the pressure is 2,200,000 N/m 2 . 4. A rectangular barge, 5 m long and 2 m wide, floats in fresh water. (a) Find how much deeper it floats when its load is a 400-kg horse. (b) If the barge can only be pushed 15 cm deeper into the water before the water overflows to sink it, how many 400-kg horses can it carry? We just have to consider the buoyant force on the barge. This is the weight of the water that is displaced. When we add a 400-kg horse, we have to displace enough water to make an additional buoyant force of 400g or 4000 N. Water density is 10 3 kg/m 3 . The new displacement of water is area x depth = 10 x depth in volume. This much water is 10 x depth x density = 10 4 x depth. The weight is g times this or 10 5 x depth. Set his equal to the 4000 N of the horse. 10 5 x depth = 4000. depth = 4000/10 5 = 0.04 m = 4 cm. We can only put three horses on (depth 12 cm). If we add the fourth, we go to 16 cm and the barge sinks.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
5. A merchant in Katmandu sells you a solid gold 1-kg statue for a very reasonable price. When you get home, you wonder whether or not you got a
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 04/01/2010 for the course PHYS 101 taught by Professor Neuhauser during the Fall '09 term at S.F. State.

### Page1 / 4

C6problems - Chapter 6 Problems 1. How much pressure do you...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online