A rock is thrown horizontally with initial velocity v from the top of a cliff of height H as shown. The rock lands at a distance D from the base of the cliff.

Question

1.If the rock were thrown from a cliff of height H' = 2H, the rock would land at a distance D' from the base of the cliff. Compare D and D'.

 

D' = sqrt(2)D
D' = 2D
D' = 4D

 

2.Suppose we know that H = 30 m and v = 20 m/s. Which of the following statements correctly describes θlanding, the angle the rock makes with respect to the ground when it lands?

 

θlanding < 45degees
θlanding > 45 degrees
We need to know the value of D in order to determine θlanding

 

 

Answer 1

For Part 1 Correct answer is sqrt 2 D . as time of fall t₂ = √2 (t₁)

 

As Height = 1/2( gt²) for free fall and assuming no air resistance

 

For part 2 tan angle = 1.2247 , So angle with horizontal is more than 45 degrees