Arock is thrown upward from the top of a 30 m building with a velocity of 5 m/s. determine its velocity (a) when it falls back past its original point, (b) when it is 15 m above the street, and (c) just before it hits the street. a horse drags a 100 kg sled a distance of 4 km in 20 minutes. the horse exerts one horsepower, of course. what is the coefficient of sliding friction between the sled and the ground?

a) 5 m/s

b) 17.8542 m/s

c) 24.7212 m/s

0.229

Explanation:

t = Time taken

u = Initial velocity = 5 m/s

v = Final velocity

s = Displacement

a = Acceleration due to gravity = 9.81 m/s²

So, the stone would travel 1.27 m up

Velocity as the rock passes through the original point is 5 m/s

Time taken to reach the original point is 0.51+0.51 = 1.02 seconds

So, total height of the rock would fall is 30+1.27 = 31.27 m

Time taken by the stone to reach 15 m above the ground is 1.82+0.51 = 2.33 seconds

Speed of the ball at 15 m above the ground is 17.8542 m/s

Speed of the stone just before it hits the street is 24.7212 m/s

F = Force

m = Mass = 100 kg

g = Acceleration due to gravity = 9.81 m/s²

s = Displacement = 4 km = 4000 m

P = Power = 1 hp = 745.7 Watt

t = Time taken = 20 minutes = 1200 seconds

μ = Coefficient of sliding friction

F = μ×m×g

⇒F = μ×100×9.81

W = Work done = F×s

P = Work done / Time

⇒P = F×s / t

Coefficient of sliding friction is 0.229

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