An Olympic skier moving at 20.0 m/s down a 30.0o slope encounters a region of wet snow, of coefficient of friction μk = 0.740. How far down the slope does she go before stopping?

a.119 m

b.145 m

c.170 m

d.199 m

Option B

Explanation:

Forces acting on the skier-

F1 down the slope  

F2

F3 = friction force    

Net force, down the slope  

Acceleration m/s2  

Acceleration remains constant, initial speed is 20 m/s

Speed at time t is m/s

Distance down the slope at time t is

When the skier stops, her speed is 0. Thus,  

, seconds

Distance travelled in 14.5 seconds (negative because it is down the slope).

Option B is correct

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =