Question

how long will a stone take to fall from a height of 80m and then what will be the velocity of stone on reaching the ground?​

Answer 1

Answer:

s=ut+1/2at^2

80m=1/2×10m/s^2×t^2

160/10=t^2

t=4 scond

Answer 2

ɢɪᴠᴇɴ :-

• Initial velocity (u) = 0m/s --(At rest)
• Height (h) = 80m
• Acceleration due to gravity (g) = 10m/s²

ᴛᴏ ғɪɴᴅ :-

• Time taken (t)
• Final velocity (v)

sᴏʟᴜᴛɪᴏɴ :-

On using 2nd equation for free falling bodies, we get,

➥ h = ut + 1/2gt²

➱ 80 = 0×t + 1/2 × 10 × t²

➱ 80 = 5t²

➱ t² = 80/5

➱ t² = 16

➱ t = √16

➱ t = 4 seconds

Hence,

• Time taken (t) = 4 seconds

On using 1st equation for free falling bodies, we get ,

➥ v = u + gt

➱ v = 0 + 10 × 4

➱ v = 40 m/s

Hence,

• Final velocity (v) = 40 m/s

NOTE :-

In the above equations,

• v = final velocity
• u = initial velocity
• t = time taken
• g = acceleration due to gravity
• h = height

• Real value of g is 9.8m/s² but sometimes to make calculation easier we use g = 10m/s²