References Mailings Review View A train travels at 42 m/s for 25 minutes. It the

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References Mailings Review View A train travels at 42 m/s for 25 minutes. It then slows to 29 m/s for the next 50 minutes then finally traveling at 22 m/s for the remaining 55 minutes. What is the Average Speed of the train in m/s 1. during this time? Remember that Average Speed- Total Distance /Total Time. Assume the changes are instantaneous so that the acceleration doesn't enter into the calculations. (28.5 m/s) The speed of light in a Farth to the Sun is 93 million miles, how long does it take (in minutes) for light from the Sun to vacuum is a constant 186,000 miles/sec. A) If the average distance from the constant 186,000 2 reach the Farth? B) Same question for the Moon Gn seconds fits average distance from the Earth is 239,000 miles. (A-8.3 min & B 1.3 s) The car traveled A ear traveling at some initial velocity accelerates at a rate of 3.2 m/s' for 18s. 215 m during this time. A) What was the car's initial velocity? B) What was the car's final velocity? (Vi--16.9 m/s & VE-40.7 m/s) 8 A plane reaches its takeoff speed of 80 m/s in 42.3 seconds. A) What it the plane's average acceleration? B) What is the distance the plane took to reach its takeoff speed? (A -1.9 m/s'& 4 B- 1684 m) 5 A meteorite strikes a car with a velocity of 600 m/s and comes to rest after leaving a 25-cm dent in is the acceleration of the meteorite? B) How long did it take to stop? (A- the hood. A) What 7.2 x 10 m/s & B-8.3 x 10's) 6 A sprinter accelerates from rest to 10 m/s in a distance of 6.5 m. A) What was her acceleration? B) How long did it take to reach her final velocity? (A -7.7 m/s & B-1.3s) from rest reaches a speed of 200 km/hr in 8.5 seconds. It then immediately starts breaking and stops in 1,5 seconds. How far did the car travel during the total time? Watch your units. (653 m) 8 Seagulls are often observed dropping clams and other shellish from a height to the rocks below to break the shells open. One particular scagull drops a clam from a height of 22 meters. A) What velocity does the clam hit the rocks with? B) How long does the clam take to fall? The acceleration due to gravity is 9.8 m/s down. (A.20.8 m/s & B-2.1 s) 9 A ball is thrown vertically downward with an initial velocity of 7.8 m/s off a 13 m-high cliff. The acceleration due to gravity is 9.8 m/s down. A) What velocity does it hit the ground with? B) How long was it in the air? Hint Watch directions. A 17.8 m/s & B-1.02 s) (US)

Explanation / Answer

1)

use,

d=v*t

==> total distance,

d=d1+d2+d3

d=v1*t1 + v2*t2 + v3*t3

d=(42*25*60 + 29*50*60 + 22*55*60)

d=222600 m

avg speed= d/toal time

=222600/((25+50+55)*60)

=28.54 m/sec

2)

speed of the light, v=186000 miles/sec

distance between the earth and sun is, d=93*10^6 miles

use,

speed=d/t

186000=93*10^6/t

==> t=500 sec or 8.33 min

and

distance between the earth and moon is, d=239000 miles

use,

speed=d/t

186000=239000/t

==> t=1.28 sec or 1.3 sec

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