Question

A basket attached to the hot air balloon has a mass of 70 kilogram upon release the balloon exerts an upwards force of 840 Newton’s on the basket. The initial upwards acceleration of the balloon and the basket is mostly nearly.
$\begin{align}
  & A.\text{ zero} \\
 & B.\text{ }2.0m/{{s}^{2}} \\
 & C.\text{ }9.8m/{{s}^{2}} \\
 & D.\text{ }14m/{{s}^{2}} \\
 & E.\text{ }30m/{{s}^{2}} \\
\end{align}$

Answer 1

Hint: It is given in the question that the balloon is going upwards hence upwards force will be greater than gravity force so that if we exclude gravitational force from upwards force we can get total net force and then by using force equation we can get acceleration of balloon attached to the basket.
Formula used: $F=ma$

Complete answer:
Given data in the question
A basket attached to the balloon has a mass of 70kg hence the gravitational force.
${{F}_{g}}=mg....\left( 1 \right)$
${{F}_{g}}$ is gravitational force, m is mass of given basket, a is gravitational acceleration
Upwards force given in the question is
${{f}_{u}}=840N$
Now in order to get the balloon in the upwards direction net force will be given by the below equation.
${{F}_{net}}={{F}_{u}}-{{F}_{g}}......\left( 2 \right)$
Now put all the formulas and values in equation (2) to get the acceleration of the balloon attached to the basket.
$\begin{align}
  & \Rightarrow ma=840-mg \\
 & \Rightarrow a=\dfrac{840-70\times 10}{70} \\
 & \Rightarrow a=\dfrac{140}{70} \\
 & \therefore a=2m/{{s}^{2}} \\
\end{align}$
Hence acceleration of the balloon that is going upwards is $2m/{{s}^{2}}$.

So the correct option is (B).

Additional information:
Newton’s second law of motion:
It states that the time rate of change of the momentum of the body is equal in both magnitude and direction to the force imposed on it.
So the acceleration can only be obtained when we apply some force on the mass for example when we ride a bicycle we apply force on pedals then the bicycle accelerates.

Note:
This hot air balloon works on a simple principle of Newton’s law of motion which suggests that, as to get a balloon in upwards direction the upwards force must be greater than gravitational force.