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The car moves in a straight line at a uniform speed of 20m / s, and the acceleration after braking is 5m / S2, then the ratio of the displacement of the car passing 2S after braking and 6S after braking is () A. 1：1 B. 1：3 C. 3：4 D. 3：1
After braking, the vehicle makes uniform deceleration movement. It is known that the initial speed V0 = 20m / s, the acceleration a = - 5m / S2, and the speed after parking v = 0. According to the speed time relationship of uniform speed change linear movement v = V0 + at, the vehicle parking time is: T = v0a = 205 = 4S; Displacement within 2S after starting braking: x2 = v0t + 12at2 = 20 × 2−12 × five × 2...
A car makes a uniform linear motion at the speed of 20m / s, and then makes a uniform deceleration linear motion at the acceleration of 5m / S2 after braking What is the ratio of the displacement of the car passing within 1s and 6S after braking? Because I don't quite understand
t=v/a=4s
S1=vt-1/2*at^2
=20-2.5
=17.5
S6=S4=vt^2/2a=400/10=40
Ratio of vehicle passing displacement within 1s and 6S after braking = 17.5/40 = 7 / 16
The car moves in a straight line at a uniform speed of 20m / s, and the acceleration after braking is 5m / s Λ 2. Then what is the displacement ratio of the car passing 2S after braking and 6S after braking?
Let the direction of uniform linear motion of the vehicle at the speed of 20m / s be the positive direction. Then a = - 5m / s Λ 2
0 = 20-5t, t = 4S. The car stops after 4 seconds. Displacement average speed method to stop (20 + 0) \ 2 * 4 = 40m
2S displacement after starting braking: 20 * 2-0.5 * 5 * 2 * 2 = 30
30：40=3：4
The car moves at a constant speed of 20m / s, and the acceleration after braking is 5 meters every 2 seconds. What is the ratio of car displacement within 2S and 6S after braking?
For this problem, you only need to pay attention to the trap of whether the car has stopped. From v = at, the maximum deceleration time is 4 seconds, so the object is still moving at the end of 2 seconds, s = vt-1 / 2at ^ 2, which is 30 meters. At the end of 6 seconds, the object has already stopped, s ` = V ^ 2 / 2a, which is 40 meters, so the ratio of two displacements is 3:4
A car with a mass of 1.2t drove onto the arc-shaped arch bridge with a radius of 50m. Q: (1) What is the pressure on the bridge when the speed of the car reaching the bridge top is 10m / S? (2) At what speed does the car just take off without pressure on the bridge when it passes through the bridge top? (3) Imagine that the radius of the arch bridge increases to the same as the radius of the earth, how fast should the car fly off on such a bridge deck? (the gravitational acceleration g is taken as 10m / S2, and the earth radius R is taken as 6.4 × 103km）
The pressure of the vehicle on the bridge top is equal to the supporting force n of the bridge top on the vehicle. When the vehicle crosses the bridge, it makes a circular motion, and the resultant force of gravity and supporting force provides a centripetal force, i.e. f = G-N; According to the centripetal force formula: F = mv2r, n = G-F = mg-mv2r = 9600N (2) when the car passes through the bridge top, there is no pressure on the bridge, then n = 0, that is, the car does
A car with a mass of 800kg drives onto the arch bridge with a radius of 50m, and the speed of the car reaching the top of the bridge is 10m / s （g=10m/s ²） Ask: (1) what is the kinetic energy of the car at this time? (2) What is the pressure of the car on the bridge
（1）40000J
(2)6400N
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- 1. A car with a mass of 800kg drives onto an arch bridge with a circular arc radius of 50m. (G is taken as 10m / S2) (l) When the car reaches the bridge top, the speed is 5m / s. how much pressure does the car put on the bridge? (2) At what speed does the car just take off without pressure on the bridge when it passes through the top of the bridge? (3) It is unsafe for the vehicle to have too little pressure on the ground. Therefore, from this point of view, the speed of the vehicle when crossing the bridge cannot be too large. For the same speed, is it safer to have a larger radius of the arch bridge arc, or is it safer to have a smaller radius? (4) If the radius of the arch bridge increases to the same as the radius r of the earth, how fast will the car fly off on the ground? (known earth radius is 6400km)
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