Determining speed in the laboratory

• There are many experiments you can do in the laboratory if you can measure the speed of a moving trolley or toy car.

Here is a image of measuring speed through light gates :

Now when the object passes through the radiation it shows the speed of the object , the object it travels through is called light gates

Rearranging equations

• As we all know Speed = Distance / time , we could also write the formula as v = s/t

• v sometimes is also known as instantaneous speed

• As we know s = d/t , this could be rearranged and could also be written as Distance = Speed into time or s = vt

• as distance even times formula is similar , Time = Distance / Speed

Questions

• An aircraft travels 900 metres in 3.0 seconds. What is its speed?

• A car travels 400 km in 3.5 hours. What is the speed of the car in km/h and m/s?

• The Voyager spacecraft is moving at 17 000 m/s. How far will it travel in one year? Give your answer in km.

• Calculate how many minutes it takes sunlight to reach us from the Sun. Light travels at 3 × 108 m/s and the Sun is about 144 million km away.

Answers

• The formula for speed is , s = d/t , thus Speed = 900 / 3 = 300 m/s

• S = d/t thus Speed = 400/3.5 = 114.28 m/s

• 536,112,000 km

• 8.3 minutes

Word problem

A cheetah can maintain its top speed of 31 m/s over a distance of 100 metres while some breeds of gazelle, such as Thomson’s gazelle, have a top speed of 25 m/s. This question considers how close the cheetah needs to be to catch the gazelle if they have both just reached top speed.

Questions

• How long does it take a cheetah to cover 100 m?

• What is the closing speed of the cheetah, that is, what is the difference in speed between the cheetah and the gazelle?

  
  

Answers

• 3.22 seconds

• The cheetah is 0.78 seconds faster than the other animal