Answer:
The speed of the block when it reaches the bottom is 17 m/s.
(b) is correct option.
Step-by-step explanation:
Given that,
Height = 15 m
Mass = 2 kg
We need to calculate the speed of the block when it reaches the bottom
Using conservation of energy
![mgh=(1)/(2)mv^2](https://img.qammunity.org/2020/formulas/physics/high-school/q4tq2cl01gkg6gs57to64i8cr5r68e7rv7.png)
![v^2=2gh](https://img.qammunity.org/2020/formulas/physics/college/n52krgpzc3zx5p6qd0iq8xmjoni6neq83u.png)
![v=√(2gh)](https://img.qammunity.org/2020/formulas/physics/high-school/o5ivb5txniqdehqlo3egp2mzj0c36o0vo8.png)
Where, g = acceleration due to gravity
h = height
Put the value into the formula
![v=√(2*9.8*15)](https://img.qammunity.org/2020/formulas/physics/college/39b6yn9t4l9v6cuxqnifx8ydym7j7peeyt.png)
![v=17\ m/s](https://img.qammunity.org/2020/formulas/physics/college/65lrrwfpzm1goyhp6r635ojdmve697p0vr.png)
Hence, The speed of the block when it reaches the bottom is 17 m/s.