Question

A car Moves with a speed of 80/km hr For 15 min and then with a speed of 60/km for next 15 min The total distance covered by the car is?

Answer 1

Answer:

Total distance covered = 35 km

Explanation:

velocity in first half v₁ = 80 km/hr = $\frac{80 X 5}{18\\}$   m/s= 200/9 m/s

velocity in second half v₂ = $\frac{60 X 5}{18}$   m/s = 60 x 5/18 = 50/ 3 m/s

time = t₁ = t₂ = 15 min = 15 x 60 sec

Distance covered in first half s₁ = v₁t₁ = $\frac{200 X 15 X 60}{9}$ =20,000 m = 20 km

Distance covered in second  half  s₂ = v₂t₂ = $\frac{50 X 15 X 60 }{3}$ = 15,000 m = 15 km

Total distance covered s = s₁ + s₂ = 20 + 15 = 35 km

Alternate Method :

Formula used :

If a body covers first half time (t) with velo v₁ and second half time with velo v₂ then

Average velo = (v₁ + v₂)/2

∴ Avg velo v = $\frac{80 + 60}{2}$  = 70 km/hr

Total time  t = 30 min = 30/60 hr = 0.5 hr

Total dist covered s = vt = 70 x 0.5 = 35 km