# Physics - Calculating Acceleration Due To Gravity

> Source: https://ollybritton.com/notes/a-level/physics/topics/calculating-g/ · Updated: 2020-10-13 · Tags: physics, kinematics, year-1, school

##### What is the _word- equation for weight??
$$
\text{weight} = \text{mass} \times \text{gravitational field strength}
$$

##### What is the _symbol_ equation for weight??
$$
W = mg
$$

##### The equation $W=mg$ is a special case of which more general formula??
$$
F = ma
$$

##### What are the two different units for $g$, the acceleration due to gravity??
$$
\frac{N}{kg} \\\\
ms^{-2}
$$

##### Which SUVAT equation would be the most useful for calculating $g$??
$$
s = ut + \frac{1}{2}at^2
$$

##### When using $s = ut + \frac{1}{2}at^2$ to calculate $g$, how can you simplify the equation??
$$
s = \frac{1}{2}at^2
$$

##### How could you rearrange $s = \frac{1}{2}gt^2$ for $g$??
$$
\frac{2s}{t^2}
$$

##### What's the simplest experiment you could perform to measure $g$ using $s = \frac{1}{2}at^2$??
Drop an object from a known height and measure the time it takes to fall.

##### If an object takes $0.1s$ to fall $1m$, how could you calculate $g$??
$$
\frac{2 * 1m}{0.1s^2}
$$

##### How could you improve the inaccurate timing of a simple drop experiment for calculating $g$??
* Use light gates
* Use a trapdoor
* Use a phone camera

##### How could you reduce the effect of air resistance in a drop experiment for calculating $g$??
Use a streamlined object.

##### Instead of doing repeats for a single height, what are the two main reasons it is better to do varying heights??
* You can plot a graph:
	* Can identify outliers
	* Drawing a line of best fit is like taking an average

##### If you wished to plot a series of displacements ($s$) and times ($t$) for a drop experiment for calculating $g$, what would your axies be??
* $s$, along the x-axis
* $t^2$, along the y-axis

##### Why is it better to plot for $t^2$ rather than $t$ when doing calculating $g$??
Because it means the graph produced will be a straight line and you can calculate $g$ by finding the gradient.

##### When using the equation $s = \frac{1}{2}at^2$ to calculate error, what are the two sources of error??
* Displacement
* Time

##### How can you ensure that the displacement is measured accurately when calculating $g$ using a drop experiment??
* Ensure the ruler is level
* Check for zero errors

##### How can you ensure that the time is measured accurately when calculating $g$ using a drop experiment??
* Use light gates
* Use metal trapdoor

##### What is more accurate, using a metal trapdoor or light gates for calculating $g$??
Using light gates.

##### What three SUVAT variables do you know when calculating $g$ using light gates??
* $s$, displacement
* $u$, inital velocity
* $v$, final velocity

##### What SUVAT equation do you use when calculating $g$ using light gates??
$$
v^2 = u^2 + 2as
$$

##### Why might an electromagnetic trapdoor method for calculating $g$ be inaccurate??
Because there may be some delay in the switch being toggled and the ball dropping.

##### What are the three methods for calculating $g$, in worst-to-best order??
1. Simple use of a timer and ruler
2. Using an electromagnetic trapdoor
3. Using light gates and a timer card

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