1-An elevator is moving downward and decreasing its speed. Which of the followin

Question

1-An elevator is moving downward and decreasing its speed. Which of the following is true?

a)the elevator's velocity points downward, and its acceleration points downward.

b)the elevator's velocity points upward, and its acceleration points downward.

c)the elevator's velocity points downward, and its acceleration points upward.

d)the elevator's velocity points upward, and its acceleration points upward.

e)the elevator's velocity points downward, and its acceleration is zero.

2-You throw a baseball toward a catcher, and it travels in an arc through the air. Ignoring any forces that the air exerts on the ball, the net force on the ball just after it leaves your hand is

a)down and away from you

b)zero

c)up and away from you

d)straight down

e)directly towards the catcher

3-When prying a board loose with a crowbar, why does it help to place your hands on the crowbar as far from the pivot point as possible?

a)the force you exert on the crowbar is greater

b)this increases your lever arm and torque

c)the resistance torque that the board exerts is decreased thereby

d)this makes the board lever arm smaller

e)the torque you must exert is decreased

4-You place a hot wet cup upside-down on a smooth counter. After it cools for a few seconds, you may find it difficult to lift up. What is holding the cup down?

a)the buoyant force on the cup

b)the heavy air inside

c)air pressure is greater inside the cup

d)air pressure is less inside the cup

e) your imagination

5-Racing bicycles often have smooth disk-shaped covers over the spokes of their wheels. That's because thin wire spokes

a) attract lighting

b)have a laminar boundary layer

c)tend to throw rocks at spectators

d)may exceed a Reynolds number of 2300 when turning

e)look ugly

6-Air conditioners are partly inside and partly outside the house becuase

a)the evaporator requires wind from outdoors

b)they are too big to fit inside the house

c)the working fluid picks up heat energy inside and carries it outside

d)the working fluid has to expel heat outside in order to work

e)the compressor it has to be inside the house to stay cool

Explanation / Answer

1)

c)the elevator's velocity points downward, and its acceleration points upward.<<<<<---answer

----------------------------

2)

the only force acting is gravitational force

d)straight down       <<<<<---answer

---------------------------

3)

torque = force * lever arm

as the torque increases it becomes easy to loosen

b)this increases your lever arm and torque <<<<<---answer

-------------------------

4)

c)air pressure is greater inside the cup

---------------------

5)

d)may exceed a Reynolds number of 2300 when turning

------------------------

6)

d)the working fluid has to expel heat outside in order to work

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