It takes 45 seconds for a bus to cross the 860 meter long bridge and 35 seconds to cross the 620 meter long tunnel at the same speed Degree

It takes 45 seconds for a bus to cross the 860 meter long bridge and 35 seconds to cross the 620 meter long tunnel at the same speed Degree

speed:
(860-620) / (45-35) = 24 (M / s)
Body length:
45 × 24-860 = 220 (m)

A motorcycle runs normally at the speed of 20 m / s. when passing through a 1000 m long tunnel, the motorcycle must pass through the tunnel at the speed of 10 m / s as required
In the process of deceleration and acceleration, the acceleration is 1 / 2m / s, and the delay time of motorcycle passing through the tunnel is calculated

The deceleration process time is (20-10) / 0.5 = 20s, the distance = (20 + 10) * 20 / 2 = 300, the original distance of 300 / 20 = 15s is now 20s, the delay time is 5S, the tunnel delay time = 1000 / 20-1000 / 10 = 50s, the acceleration is 5S as the deceleration, so the tunnel delay time is 60s

A truck leaves a station at a speed of 10m / s. after driving for 2 hours and 15 minutes, a motorcycle chases the truck from the same station at a speed of 48km / h
(1) The time it takes for a motorcycle to catch up with a truck; and (2) the distance to the station

2h15min = 2.25 hours
10m / S = 36 km / h
We have walked 36 * 2.25 = 81 km
The time it took the motorcycle to catch up with the truck
81 / (48-36) = 81 / 12 = 6.75 hours
）Distance from the station when catching up
48 * 6.75 = 324km