An introduction to exoplanets
An introduction to exoplanets

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

4.1  Velocity and speed

Speed is a measure of how fast something is moving. Velocity is also a measure of how fast something is moving, but when talking about velocity the direction is important as well.

Imagine standing in the middle of a bridge above a UK motorway watching the cars. Assume everyone is obeying the speed limit and driving at exactly 70 miles per hour. Everyone is therefore travelling at the same speed, but the cars on opposite sides of the road are travelling in opposite directions. Everyone on the left, travelling away from you, has a velocity of 70 mph, but everyone on the right and travelling towards you has a velocity of minus 70 mph, so they are travelling at the same speed as the drivers going away from you, but in the opposite (negative) direction (Figure 4).

Described image
Figure _unit4.4.1 Figure 4  Motorway velocity diagram. Velocity includes information about direction of motion as well as speed, so the cars on the left have a velocity of 70 mph but the cars on the right have a velocity of −70 mph

Direction of motion is very important when measuring wobbling stars, as you will see in the next section.

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371