Can you jump a motorcycle into space?

[This question and answer are intended as an example of part of a tutorial on the conservation of energy for an A-Level physics student.]


A daredevil is planning the ultimate feat: jumping a motorcycle into space from a standstill. How big does her fuel tank need to be?

Assume the following:

Space begins at 100 km above sea level.

The acceleration due to gravity is 9.81 ms-2 regardless of altitude.

The energy density of fuel is 50 MJ/kg.

The motorcycle and rider together weigh 500 kg.

No energy is lost by the rider and motorcycle to the surroundings.


The simplest way to tackle this problem is by conservation of energy. As with most problems of this type, we’ll look separately at the initial situation and the final situation, then assume no energy is lost in between.

Initial situation:

The motorcycle, rider and fuel are at sea level. Call the mass of the motorcycle and rider together m, and the mass of the fuel M. The only energy in the system is the chemical energy U of the fuel:

Einitial = U,

and U = uV,

where u is the energy density of the fuel and V is its volume.

Final situation:

If the rider only just reaches her goal, then she and the motorcycle only just reach the 100 km level before falling back to Earth. At that point, there is no fuel left, and they are still for just an instant. Therefore the only energy in the system is then the gravitational potential energy of the rider and motorcycle:

Efinal = mgh,

where h = 100 km.

Conservation of energy:

Because no energy was lost to the surroundings, we have Efinal = Einitial, so:

U = mgh,


uV = mgh.

We want the volume of the fuel tank, so:

V = mgh/u.

Substituting in all the values, we obtain:

V = (500 kg)(9.81 ms-2)(100 km) / (50 MJ/kg)

Which evaluates to:

V = 9.8 m3 = 9,800 L.

Gabriel V. GCSE Physics tutor, A Level Physics tutor, Mentoring Physi...

2 years ago

Answered by Gabriel, an A Level Physics tutor with MyTutor

Still stuck? Get one-to-one help from a personally interviewed subject specialist


£36 /hr

James G.

Degree: Mathematical Physics (Doctorate) - Nottingham University

Subjects offered:Physics, Maths+ 2 more

Further Mathematics

“Currently a 3rd year PhD student in Mathematical Physics. I'm very passionate about teaching as well as my subject area. Look forward to hearing from you.”

£22 /hr

Max G.

Degree: Mathematics and Physics (Masters) - Durham University

Subjects offered:Physics, Maths+ 1 more

Further Mathematics

“I am a maths and physics student at the University of Durham, for as long as I can remember i have been obsessed with all things science! I am patient, friendly and most of all understanding to the fact that the sciences aren't for ev...”

PremiumJames L. A Level Biology tutor, A Level Chemistry tutor, GCSE Biology...
£26 /hr

James L.

Degree: Medical Sciences (Bachelors) - Exeter University

Subjects offered:Physics, Science+ 3 more


“Hi, I'm James, a Masters student studying Biology. I'm really passionate about science, and I hope i can share some of it with you! ”

About the author

£30 /hr

Gabriel V.

Degree: DPhil in Biological Physics (Doctorate) - Oxford University Alumni University

Subjects offered:Physics, Maths+ 2 more

Further Mathematics
-Personal Statements-

“Top tutor from the renowned Russell university group, ready to help you improve your grades.”

MyTutor guarantee

You may also like...

Other A Level Physics questions

How do I resolve forces on a slope?

Why is the centripetal force necessary for circular motion?

Why does a single slit diffraction pattern occur?

A car is travelling at 10m/s when it brakes and decelerates at 2ms^-2 to a stop. How long does the car take to stop?

View A Level Physics tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss