At each site, the scientists measure several physical quantities. Complete Table 1.1 by giving the SI base unit for each quantity and by ticking (✓) whether each one is a scalar or a vector. Use the working space if needed.
At one site, the air density is $1.1\,\text{kg m}^{-3}$. A spherical weather balloon is filled with gas and then released from rest. The balloon has radius $0.90\,\text{m}$. Calculate the upthrust acting on the balloon at the moment it is released.
Explain why the balloon experiences an upthrust.
The balloon’s weight is $19\,\text{N}$. Calculate the magnitude of its initial acceleration.
A quantity $c$ connected with the balloon’s motion is determined from three measured quantities $k$, $F$ and $v$ using $c = \dfrac{2kF}{v^2}$. The percentage uncertainties in the measured quantities are listed in Table 1.2. The calculated value of $c$ is $1.8$. Determine the absolute uncertainty in $c$.