A 1.0 kg rock is thrown straight upward with an initial speed of 8.0 m/s. What is its speed

When it reaches a height of 1.6 m?

Answer:5.7m/s

Explanation:

Mass=1kg

Initial velocity=u=8m/s

height=h=1.6m

Final velocity = v

Acceleration due to gravity=g=9.8m/s^2

v^2=u^2-2xgxh

v^2=8^2-2x9.8x1.6

v^2=8x8-2x9.8x1.6

v^2=64-31.36

v^2=32.64

Take the square root of both sides

√ (v^2) = √ (32.64)

v=5.7

Speed at the height of 1.6m is 5.7m/s