Physics Unit 9 States of Matter Review

Which of the following statements about floating objects is correct?

The buoyant force is greater than the force of gravity

If an object is only partially submerged in a fluid, which of the following is true?

The density of the fluid is greater than the density of the object

Which of the following statements is true.

Pressure on a submerged object is greatest at the bottom of the object

Which of the following statements is always true?

Pressure always increases when force increases or the area acted on decreases

Why does the lift on an airplane wing increase as the speed of the airplane increases?

The pressure above the wing becomes less than the pressure below the wing

Where is the pressure greater, one meter beneath the surface of Lake Michigan or one meter beneath the surface of a swimming pond?

The pressure is approximately the same in both places

The reason a life jacket helps you float is that _______.

you and the jacket together have a density less than your density alone

If an object has a density equal to the density of water, it will _______.

neither float nor sink, but stay anywhere it is put

A block of balsa wood floats on water while a block of lead the same size lies submerged in the water. The buoyant force is (Hint. VeV. when an object is floating (partially submerged))

greater on the lead

When a boat sails from fresh water to salt water, the boat will float _______.

higher in the salt water

Pascal's principle says that changes in pressure at any point in an enclosed fluid

are transmitted to all points in the fluid

A hydraulic arrangement consists of a water-filled U-tube that is wider on one end than on the other. Pistons are fitted in both ends. To multiply an input force, the input end should be the one having the ______.

smaller-diameter piston

Air pressure in a tire depends on _____.

all of these

Boyle's law relates ______.

pressure and volume

A balloon is buoyed up with a force equal to the ______.

weight of air it displaces

A bubble of air released from the bottom of a lake ______. (Hint. Boyle’s Law)

becomes larger as it rises

An umbrella tends to move upward on a windy day because _______.

a low-pressure area is created on top of the umbrella

A dam is thicker at the bottom than the top partly because

Water pressure increases with depth

A Pascal is equal to which of the following units (Hint. Pressure-Force/Area)

Newton/ square meter

Atmospheric pressure is caused by the __________, which causes the particle to become packed with ___________

density at Earth's surface

Weight of the atmosphere, more

Vo= Vf when objects float on top of the water

False

A suction cup sticks to the wall because the force of vacuum holds it there

False

As velocity of a fluid decreases, pressure decreases

False

When the buoyant force is greater than the force of gravity on an object it will float

True

A perfectly circular swimming pool is 4.0 m in radius and 3.0 m deep. What is the pressure exerted on the bottom surface of the pool? What is the force exerted on the bottom surface of the pool? The pool is filled with fresh water. (rH2O= 1000 kg/m3)

Ptotal= 101,325+1000(9.80)(3.0)= 130,725~130,000 Pa, P= F/a, F= 130,725(π4.00^2)= 6,570,955~ 6.6x10^6 N

A hydraulic car lift with square shaped reservoirs is used to raise a car. The length and width of the input piston are 1 m and has a negligible weight. The output piston has a total area of 20 m2. The combined mass of the car and the output piston is 1800 kg. What force should be applied to the input piston to raise the car?

F1= F2(A1)/A2, 1800(9.80)(1)/20= 882 N

A hydraulic car lift is used to raise a car. The radius of the input piston is 0.0120 m and has a negligible weight. The output piston has a radius of 0.150 m. The combined mass of the car and the output piston is 1800 kg. What force should be applied to the input piston to raise the car?

(1800)(9.80)(π)(0.0120^2)/(π)(0.150^2)= 112.896~ 110 N

1. When the force of gravity is stronger than the buoyant force an object will (sink, float)

3. When the buoyant force is greater than the force of gravity an object will (sink, float)

1. sink

3. float

A bar of an unknown metal has a length of 0.975 m at 45 oC and a length of 0.972 m at 23 oC. What is its coefficient of linear expansion?

a= lf-li/li(tf-ti), a= 0.975-0.972/0.972(45-23)= 1.40x10^-4

An aluminum sphere is heated from 11 oC to 580 oC. If the volume of the sphere is 1.78 cm3 at 11 oC, what is the increase in sphere volume at 580 oC? Β = 69x10^6

vi(tf-ti)B= vf-vi, 1.78(580-11)(69)= vf-vi, vf-vi= 69,884.58~ 0.70 cm^3