Question

a ball is dropped from the top of the building it requires a velocity of 80m/s-² on reaching the ground. calculate the height of the building.take g=10m/s-​

Answer 1

To find:-

• The height of building

Solution:-

As the ball will fall down a constant acceleration will act on ball downwards which is due to gravitational force. Hence we can apply 3 equations of motion.

In simple words we can find the height of building using three equations of motion.

Using 3rd equation will be appropriate here

$\large \: \mathsf{{v}^{2} - {u}^{2} = 2as}$

as body starts falling from top hence initial velocity is zero. Final Velocity is given 80m/s and acceleration we already know is 10m/s²

Hence putting the values:-

$\large\rightarrow \mathtt {{(80)}^{2} - {0}^{2} = 2 \times 10 \times s }$

$\large \rightarrow\mathtt {6400= 20\times s }$

$\large \rightarrow\mathtt { \frac{6400}{20} = s }$

$\large\rightarrow \mathtt{s = 320m}$

Note that:-

• V=Final velocity
• U=Initial velocity
• a= acceleration
• s=height of building