Which of the following would you use to accurately measure the time taken for a car to travel 20.0 m?

Option A is wrong. The car actually moves a greater distance than 20.0 m.

Option B, Option C and Option D are all showing the car moving a distance of 20.0 m. So, are they equally valid ways to measure the time, or does any method have an advantage?

 

Most people will find it significantly easier to time using Option B. It is easy to identify exactly when the car starts to cross a line.

 

Transferring this over to the marble on the ramp practical, we can see that the following would be the preferred start and end positions of the marble:

In practice, a block placed at the end of the track allows for an even clearer indicator as to when the marble has completed travelling 90.0 cm. We can use the sight of the marble hitting the block and/or sound of the collision as additional guides as to when to accurately stop the stopwatch.

 

Practical Skills