A 50.0kg rock in the Nahanni River canyon breaks loose from the edge of a cliff and falls 500m into the water below. The average air resistance is 125N.

a) What is the average acceleration of the rock?

b) How long does the rock take to reach the water?

c) What is the true weight of the rock?

d) Does the rock have an apperant weight? explain your responce.

 

a) Average acceleration of the rock = 7.3 m/s²

b) Time taken by the rock to reach the water = 11.704 second

c) True weight of the rock = 490 N

d) Yes the rock will have an apparent weight as the surrounding air will exert a buoyant force due to air friction in the upward direction. Whereas, the weight of the object will act downwards.

So the expression is as follows,

Net force(Apparent weight) = True weight - Buoyant force.

Step-by-step explanation

a) Calculation of the average acceleration of the rock

Average Acceleration = Downward acceleration - Upward acceleration

Note : Downward acceleration = 9.8 m/s² ; Upward acceleration = buoyant force / mass of the rock

Average Acceleration = 9.8 m/s² - ( 125 N / 50 kg ) = 9.8 m/s² - 2.5 m/s² = 7.3 m / s²

b) Calculation of the time taken by the rock to reach the water

s = ut + ( 1/2 a_Average * t² ) ; Note : u = 0.

500 metre = 0 + 1/2 * 7.3 * t²

t² = 136.98

t = 11.704 second

c) Calculation of the true weight of the rock

True weight of the rock ( w ) = m * g ( where g = 9.8 m/s² )

True weight of the rock = 50 kg * 9.8 m/s² = 490 N