It has been said that in his youth george washington threw a silver dollar across a river. assuming that the wide, (a) what minimum initial speed river was 75 m was necessary to get the coin across the river and b) how long was the coin in flight?

minimum initial speed was 27.11 m/s

coin in flight was 3.91 seconds

Explanation:

wide = 75 m

to find out

what was minimum initial speed and timer for coin in flight

solution

we know that speed will be minimum when angle is 45 degree so

we will use here equation of parabolic that is

so

distance =   ...............1

here distance is 75 m and a is angle i.e 45 and g is 9.8 m/s² and v is speed

75 =

v = 27.11

minimum initial speed is 27.11 m/s

and

we know time for coin in flight formula is

time =   ...............2

here v is speed and g is acceleration 9.8 and a is angle 45 degree

so

time =  

time = 3.91

so coin in flight was 3.91 seconds

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s