Question

stone is shot straight upward with speed 20m per sec from tower 200 m high find the speed with which strikes the ground ??

Answer 1

Answer:

• Stone will strike the ground with a velocity = 20√11 m/s.

Explanation:

A stone is thrown upward from a 200 m high tower with an initial velocity of 20 m/s

Firstly considering case when Stone is thrown upward. so, its final speed at the highest point will be zero and acceleration due to gravity will be -10 m/s²

so,

• initial velocity = 20 m/s
• final velocity = 0
• Acceleration due to gravity = -10 m/s²  [ negative because stone is going upwards]
• Let, distance covered by stone going upward = s

so,

Using third equation of motion

→ 2 a s = v² - u²

[ a is acceleration, s is distance, v is final velocity, u is initial velocity ]

→ 2 ( -10 ) s = ( 0 )² - ( 20 )²

→ -20 s = - 400

→ 20 s = 400

→ s = 20 m

so, distance covered by stone going upward is 20 metres.

Further,

Stone will start falling down, with initial velocity zero, acceleration due to gravity 10 m/s². and since, it is ( 200 + 20 ) metres above the ground, therefore, for reaching to the ground it will cover distance 220 m.

so,

• Initial velocity = 0
• distance to be covered = 220 m
• Acceleration due to gravity = 10 m/s²
• let, final velocity of stone with which stone will strike the ground = v

then,

Again, Using third equation of motion

→ 2 a s = v² - u²

→ 2 ( 10 ) ( 220 ) = v² - ( 0 )²

→ 4400 = v²

→ v = 20√11  m/s

therefore,

• Stone will strike the ground with a velocity of 20√11 m/s .

Answer 2

Answer:

refer to the attachment