Question

Equation of motion for free fall can be used in case of any free fall.

• A. True
• B. False

Answer 1

The correct option is B False

Equations of motion of a freely falling body:

In the case of a freely falling body, the acceleration of the body is equal to the acceleration due to gravity.

Therefore, $a=g$

General equations of motion are

$$\begin{gathered} v=u+at \\ s=ut+\frac{1}{2}a{t}^2 \\ {v}^{2\_}{u}^2=2as \end{gathered}$$

Replace $a=g$ and $s=h$.

Thus, the equations of motion for free fall are

$$\begin{gathered} v=u+gt \\ h=ut+1/2g{t}^2 \\ {v}^{2\_}{u}^2=2gh \end{gathered}$$

Equations of motion for free fall are invalid in some situations like,

1. If there is air resistance then it may make the value of accelerations different for different objects.
2. If there are any effects due to the rotation of the earth then it may also make the accelerations different.
3. The equation of motion for free fall is applicable only when $\text{'}g\text{'}$has a constant value. Acceleration due to gravity $\text{'}g\text{'}$has a constant value near the earth's surface.
4. If the height of the body is comparable to the radius of the earth then $\text{'}g\text{'}$changes. In such a case equation of motion are not valid.

Hence, the statement is false.