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From Jinan to Beijing, the actual distance is 490 km. The distance between the two places measured on a map is 4.9 cm
scale
=4.9 cm: 490 km
=4.9：49000000
=1：10000000
What is the speed of the point where the tire contacts the ground in an instant when driving on a horizontal road
And the instantaneous speed in the middle of the tire
At the point where the tire contacts the ground, the instantaneous speed is 0. This point is static relative to the ground and receives static friction from the ground. Moreover, the direction of friction at this point is forward and pushes the car forward
The speed of the center of the tire is the speed of the car
The length of a highway is 2512m, the outer diameter of a car's tire is 1m, and the driving time on the bridge is 20 seconds
How many turns did the wheel roll on the bridge?
Formula
V=2512/20=125.6(m/s)
Rockets are not so fast
2512 / (1 * 3.14) = 800 (circle)
On the straight road, the vehicle with the speed of V = 12m / s advances at a constant speed. In case of emergency, after braking, the tire stops rotating and slides on the ground. After the time t = 1.5s, the vehicle stops, and the local gravity acceleration g is taken as 10m / s
Solution: 1. The acceleration a of the car when braking
2. The displacement X of the car within 1 s after starting to brake
3 dynamic friction coefficient between tire and ground when braking
1. According to ν = at, a = ν / T = 12 △ 1.5 = 8m / S & sup2;
2.S＝ν-at²／2＝8m
3. According to a = & micro; G, we can deduce & micro; = A / g = 8 △ 10 = 0.8
RELATED INFORMATIONS
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