Join The Parade, New South Wales - Ph:+61-2-1234-5678


DATE TBA: A classroom visit by Professor Yourname Backwards from the planet Voltaren

Next week, Professor Newsy Wales is expecting a visit from his twin brother, Professor Selaw Yswen.

Professor Selaw Yswen at home

Image 1. Professor Yourname Backwards from planet Voltaren says: “I'm looking forward to visiting WPS scientists”

Professor Selaw is from planet Voltaren and so he knows nothing about how gravity works on Earth.

There is a rumour that aliens on another planet (planet Placebo), are working on a huge gravity powered nerf launcher that they will use to try to blast a hole right through the centre of planet Voltaren.

The people of Voltaren are worried about this and want to find out as much as they can about any potential damage.

Professor Newsy Wales suggested that, as experts in the field, the WPS scientist students help Professor Selaw understand everything that Voltarens need to know about gravity and projectiles:

On his visit, Professor Yourname Backwards would like to find out:

  1. What is the optimal range of a nerf launcher when it is fired on the Earth.
  2. What would it be like falling through a hole in the centre of the Earth
  3. How would these effects be different on other planets (say a planet where gravity is only one half (1/2) of the gravity on Earth)


  1. Is the Nerf launcher/gun and protractor system used in previous school science activities still available in school somewhere?


Weekly science facts that your friends probably do not know about.


Voltaren Defenders Trajectory Map

Fig 1. Nerf Projectile Trajectory Maps:


The Placebans were on a journey back to their home planet when they became trapped by the gravity of planet Voltaren. The planet Placebo has now become trapped in a spiral orbit around the planet Voltaren.

Planet Placebo has almost no gravity and the Placebans believe that if they blast a hole trough the centre of planet Voltaren, their planet will break free from Voltaren and they will continue on their journey.

The Placebans plan to fire a nerf bomb (projectile) from point A on planet Placebo, to strike at point B on planet Voltaren.

A correctly positioned projectile landing at point B will create a hole through planet Voltaren from point B to point C.


Because their orbit is not an exact circle, the Placebans have a number of different places they can launch their missile from… but time and distance is critical.

Your mission, should you choose to accept it, is to use gravity simulator software to punch in the data below and find the best place for the Placebans to fire their missile while minimising the damage for those on Voltaren.


Unfortunately, after the projectile hits, any Voltarens who stand too close to point B will fall through the hole - Not so good for them! Placeban scientists are unsure what effect this will have, and so we will ask you to guess what might happen to any such unfortunate Voltarens who fall into the hole.

Any projectiles falling outside the target range may harm puppies - The Placebans do not want to harm any puppies!



Your mission is to run experiments and find the missing numbers in Table 1. (below)

  • Assume that the gravity of planet Voltaren is the same as gravity on the Earth.
  • Planet Placebo is has no significant mass/gravity itself, but is affected by the gravity of planet Voltaren. When entering data in the gravity simulator, think of planet Placebo as if it were just a very high mountain on planet Voltaren.
  • Check out the measurements in the table below (especially height and range)
  • Enter the data from Table 1. into your simulation software and fill in the missing values (replace the question marks '?' in Table 1.).
  • Approximate values are OK - Do as much as you can: this is NOT a test :)
  • If you need more help, read the 'NOTE:' section below Table 1.

Voltaren Trajectory Plan

Launch velocity Launch Angle Launch Height (+ or -)* Range (horiz. dist.)Time
10m per sec 45 degrees -10 metres ?
100m per sec 45 degrees -100 metres ?
200m per sec 45 degrees -1000 metres (1km) ?
400m per sec 45 degrees -10000 metres(10km) 23,??? metres 8?.? s
400m per sec 40 degrees -10000 metres(10km) 2?,??? metres ??.? s
400m per sec 34 degrees -10000 metres(10km) 2?,??? metres ??.? s
400m per sec 30 degrees -10000 metres(10km) 2?,??? metres ??.? s
NOTE:Do not enter commas

Table 1. Placebo to Voltaren (Launch data with settings based on Fig 1.):

  • *NOTE: The 'Launch Height' is the difference in height between the surface that the nerf gun is fired from (planet Placebo), compared with the height of the surface that it will land on (planet Voltaren): Depending on the calculator that you use, you may need to enter the height as a minus or a plus value.
  • For the above calculations, we used the Where Will It Land - HyperPhysics Calculator, which is designed for calculating ranges in situations where the launch point is not at the same level as the landing point (there is a simplified, working version that you can use at the bottom of this page)
  • Any of the other calculators (listed above) should return similar (good enough for this challenge) results, and may be easier to use.


This is an optional 'extra' - for any scientist seeking a challenge:

  • At the maximum part of their orbit, point A on planet Placebo is one hundred kilometeres (100,000m or 100km) higher than the surface of planet Voltaren: point B.
  • The maximum launch velocity of the Placebo nerf gun is four hundred meters per second (400mps)
  • To avoid possible errors resulting from unreliable components and calculations, the nerf missile must not take more than one hundred and sixty seconds (160s) to reach point B.
  • The horizontal distance (the Range)from A to B is around fifty nine and a half kilometres.
  • To be successful, the actual range of the nerf missile must fall between 59.3 and 59.5 kilometres - otherwise the missile will fail to create a hole through the centre of the planet.
  • The attackers have calculated most of the values that they will use to plan their attack - your mission is to enter the missing numbers:

The stuff above may sound complicated but you only have to take the values from the table and plug them into the simulator software.

The challenge is to consider the results and match them to the requirements:

To find the answers, enter the values for each trial launch (Trials 1 to 5) from Table 2. into your chosen gravity simulator software.

TrialsLaunch velocity Launch Angle Launch Height (+ or -)* Range (horiz. dist.)Time
1400m per sec 45 degrees -100000 metres (100km) ??,??? metres 1??.? s
2400m per sec 40 degrees -100000 metres (100km) 5?,??? metres 1??.? s
3400m per sec 20 degrees -100000 metres (100km) 5?,??? metres 1??.? s
4400m per sec 15 degrees -100000 metres (100km) 5?,??? metres 1??.? s
5400m per sec 10 degrees -100000 metres (100km) 5?,??? metres 1??.? s
NOTE: Do not enter commas!

Table 2. Finding the optimal launch angle:

In case you have problems viewing calculator try this link or here

events/visiting-alien-day/home.txt · Last modified: 21/12/2016/ 22:27 by