A stone is dropped vertically downwards from the top of a tower of height 45m with a speed of 20m/s. find the; (a) time it takes to reach the ground.
(b) speed with which it hits the ground.
( take g=10m/s)

(a) 1.6 s

(b) 36 m/s

Step-by-step explanation:

Take down to be positive.

Given:

Δy = 45 m

v₀ = 20 m/s

a = 10 m/s²

(a) Find t.

Δy = v₀ t + ½ at²

45 m = (20 m/s) t + ½ (10 m/s²) t²

45 = 20t + 5t²

9 = 4t + t²

13 = t² + 4t + 4

13 = (t + 2)²

t = -2 ± √13

t ≈ 1.6 s

(b) Find v.

v² = v₀² + 2aΔy

v² = (20 m/s)² + 2 (10 m/s²) (45 m)

v = 10√13

v ≈ 36 m/s

given that triangle abc is transformed two times to get triangle

a"b"c"

first abc is transformed in to a'b'c' as follows:

the coordinates of a are (1,-1) and transformed into a'(-1,1)

similarly b (4,-2) became b'(-4,2) and

c(7,-2) became c'(-7,2)

i.e. (x,y) becomes (-x,-y)

this is nothing but reflection about a point here origin.

thus first transformation is reflection on the origin.

next is exactly shifting 3 units down

source:

step-by-step explanation: