Physics - Calculating Acceleration Due To Gravity

Created: October 13, 2020

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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