Athletic competition

In a 400 meter athletic competition, a participant covers the distance as given below.
find the average speed?

first 80 meters 10 m/s
next 240 meters 7.5 m/s
last 80 meters 10 m/s

Correct result:

v =  8.3333 m/s

Solution:

$$\begin{gathered} s=vt \\ {s}_1=80\text{ m } \\ {s}_2=240\text{ m } \\ {s}_3=80\text{ m } \\ {v}_1=10\text{ m/s } \\ {v}_2=7.5\text{ m/s } \\ {v}_3=10\text{ m/s } \\ {t}_1=s_1\mathrm{/}{v}_1=80\mathrm{/}10=8\text{ s } \\ {t}_2=s_2\mathrm{/}{v}_2=240\mathrm{/}7.5=32\text{ s } \\ {t}_3=s_3\mathrm{/}{v}_3=80\mathrm{/}10=8\text{ s } \\ v={\displaystyle \frac{s_1+s_2+s_3}{t_1+t_2+t_3}}={\displaystyle \frac{80+240+80}{8+32+8}}={\displaystyle \frac{25}{3}}=8.3333\text{ m/s} \end{gathered}$$

Try another example

Showing 0 comments:

Next similar math problems:

• Collision
  The two bodies, whose initial distance is 240 m, move evenly against each other consistently. The first body has an initial velocity of 4 m/s and an acceleration of 3 m/s², the second body has an initial speed of 6 m/s and an acceleration of 2 m/s². Fin
• Two cities
  Cities A and B are 200 km away. At 7 o'clock from city A, the car started at an average speed of 80 km/h, and from B at 45 min later the motorcycle is started at an average speed of 120 km/h. How long will they meet and at what distance from the point A i
• Fog
  The car started in fog at speed 30 km/h. After a 12-minute drive, the fog dissipated and the driver drove next 12 minutes distance 17 km. On the last 17 km long again the driving conditions deteriorated and the driver drove the speed of 51 km/h. a) Calcul
• Express train
  International express train drove from Kosice to Teplice. In the first 279 km, the track was repaired, and therefore it was moving at a speed of 10km/h less than it was scheduled to drive. The rest of the 465 km trip has increased the speed by 8 km/h than
• The shooter
  The shooter heard the impact of the bullet on the target in one second after the shot. The bullet was moving at an average speed of 500 m/s. Calculate with speed of sound of 340 m/s. Determine the distance of the target.
• Acceleration
  The car accelerates at rate 0.5m/s². How long travels 400 meters and what will be its speed?
• Average
  What is the average speed of the car, where half of the distance covered passed at speed 66 km/h and the other half at 86 km/h.
• Free fall
  The free fall body has gone 10m in the last 0.5s. Find the body speed at the moment of impact.
• Transformer
  Solve the textbook problems - transformer: a) N1 = 40, N2 = 80, U2 = 80 V, U1 =? b) N1 = 400, U1 = 200 V, U2 = 50 V, N2 =?
• Average speed
  The car drove from city A to city B at a speed of 40 km/h and back to city A at a speed of 80 km/h. What was the average speed of the car?
• Motion
  From two different locations distant 232 km started against car and bus. The car started at 5:20 with average speed 64 km/h. Bus started at 7:30 with average speed 80 km/h. When they meet? How many kilometers went the bus?
• Two airports
  Two airports are 2690 km away. From the first airport, the airplane flies at a speed of 600 km/h, from a second airplane at a speed of 780 km/h. When will they meet if they flew at 10:00? How far from the first airport?
• Dried fruit
  The manufacturer produces a mixture of dried fruit. He purchased: 10kg pineapple for 200 Kc/kg 2kg papaya for 180 kc/kg 1kg of banana for 400 Kc/kg How many kgs of raisin for 80 Kc/kg must be put into the mix by the manufacturer so that the production pri
• Car - road
  Car started at 11:40 at speed 54 km/h from A and to B arrived at 12:20. Determine the distance A and B.
• Sprinter
  Sprinter runs the relay 4 x 400 m to the handover at speed 42 km/h. A second runner is at the start of the handover area 20 m long and runs when it is the first sprinter at distance 10 m. Calculate the speed at which the second runner must run in order to
• Annual income
  The annual incomes (in thousands of $) of fifteen families is: 60, 80, 90, 96, 120, 150, 200, 360, 480, 520, 1060, 1200, 1450, 2500, 7200 Calculate harmonic and geometric mean.
• Speeds
  George pass on the way to school distance 200 meters in 165 seconds. What is the average walking speed in m/s and km/h?