![](data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 72 71" width="72"></svg>)
The acceleration of a car is 6m / S2 when it is in emergency braking on a road. If it has to stop within 2S, the maximum speed of the car can not exceed () A. 10m/sB. 12m/sC. 14m/sD. 13m/s
According to the reverse thinking, if the car moves in a straight line with uniform acceleration and zero initial speed, then v = at = 12m / s
A car runs 23 miles along the straight road at the speed V1, and then runs the remaining 13 miles at the speed V2 = 20km / h. If the average speed of the car for the whole journey is 28km / h, what is the speed of the car in the first 23 miles?
Suppose the whole journey is x, the average speed formula can calculate the time of the whole journey and the last 13 journey is t = XV, T2 = X320, then the time of the first 23 journey is T1 = t-t2 = xv-x320 = x28-x60 = 2x105 & nbsp; & nbsp; & nbsp; & nbsp; so V1 = 2x3t1 = 35 & nbsp; km / h, a: the speed of the first 23 journey is 35 km / h
Two straight roads intersect at an angle A. two cars drive along the two roads at the speed of V1 and V2 respectively. What is the speed of one car relative to the other?
Take one of the cars as the reference object, you might as well choose v1. Because the speed direction of the two cars is vertical, the other car relative to the reference object has not only the original V2 speed, but also a - V1 speed (because the direction is opposite), so the combined speed is the vector sum of V1 and V2, and its size is the square sum of V1 and V2 and then the root, that is, the square of V1 under the root plus the square of v2
RELATED INFORMATIONS
- 1. When a car runs on a straight road, its speed is V1 in the first half of the time and V2 in the second half Find the average speed of the car in this period
- 2. [physics of senior one] If an object moves in a straight line in the same direction, the first half of the distance is V1, and the second half is V2, then the average speed of the whole course is 0____ When an object moves in a straight line in the same direction, the first half of the distance velocity is V1, and the second half of the distance velocity is V2, then the average speed of the whole course is 0________ . I did. The answer is 2v1v2 / V1 + v2
- 3. When an object moves in a straight line with constant speed change, its speed when it passes through the middle of the whole journey is V1, and its speed at the middle of the whole journey is v2?
- 4. A hare was playing on the grass at a distance of 200m from the cave S1, and was chased by the hound at the maximum speed. When the rabbit found the hound, it was 60m away from the hound, and the rabbit immediately ran to the cave, At least what is the acceleration of the hare in order to return to the cave safely
- 5. The maximum running speed of the Hound is 30m / s, and the running speed of the hare is 72km / h. how long does it take for the hound to capture a hare with the first 20m?
- 6. The hound catches up with the hare 30 meters ahead. The hound has a big step. It runs 4 steps. The hare runs 7 steps, but the hare moves fast. The hound runs 3 steps faster than the hare Please answer if you know
- 7. When a boat crosses the river, the width of the river is 180 m and the velocity of the current is 3 M / s When a boat crosses a river, the width of the river is d = 180m, and the current velocity is V1 = 3m / s. if the speed of the boat in still water is V2 = 5m / s, it is known that sin53 degree is equal to 0.8 and cos53 degree is equal to 0.6. What direction should the bow of the boat cross the river in the shortest time and what is the shortest crossing time
- 8. Volume of solution after mixing V1 ml water and V2 ml alcohol___ (V1 + V2) ml (> or
- 9. We know an undirected graph G = (V, e), where V = {V1, V2, V3, V4}, and its adjacency matrix is as follows
- 10. When the same amount of sodium, magnesium and aluminum react with sufficient hydrochloric acid, the volume ratio of hydrogen released is? The same amount of sodium, magnesium and aluminum react with sufficient hydrochloric acid
- 11. 1. The original speed of the locomotive is 36km / h, and the acceleration is 0.2m/s on a section of downhill road. When the locomotive runs to the end of the downhill, the speed increases to 54km / h. find out the time for the locomotive to pass this section of downhill road 2. The train should slow down in advance when passing through bridges and tunnels. A train running at a speed of 72km / h decelerates at a constant speed when entering a stone arch bridge. It decelerates for 2min, and the acceleration is 0.1m/s ^ 2. What is the speed of the train after decelerating?
- 12. A and B students practice the 4 × 100 meter relay on the straight track. They have the same maximum speed when running. B starts to run with all his strength from a standstill A. B two students practice 4 times 100 relay on the straight. They have the same maximum speed when running. B runs with all his strength from a standstill. It takes 25 meters to reach the maximum speed, This process can be regarded as uniform variable speed movement. Now a is running to B with the maximum speed. B is waiting for the opportunity to run out in the relay area. If B is required to run at 80% of the maximum speed when taking over the baton, Q: 1: what is the distance S1 that B needs to run in the relay area? 2: what is the distance S2 that B needs to run from a?
- 13. The students all like to watch "pleasant goat and grey wolf". One day, pleasant goat found that grey wolf was rushing towards him at the speed of 15mgs at 100m behind him. At this time, pleasant goat was 200m away from the sheep village in front of him. Question: at least how fast does pleasant goat need to run into the sheep village safely?
- 14. In the 100 meter race, the athlete ran 80 meters at the speed of 8 m / s, and then ran 20 meters at the speed of 2 m / s to find the average speed of the road But the answer is 5.5m/s
- 15. Given that s is the same, V1: V2: V3 = 2:3:5, find T1: T2: T3
- 16. When Kramer rule is used, what is the solution of the system of equations when d = 0? I want to know how to deduce rank less than n from D = 0
- 17. Linear algebra solves this problem! Cramer's law Find the cubic polynomial f (x) = A0 + a1x + a2x ^ 2 + a3x ^ 3, such that f (- 1) = 0, f (1) = 4, f (2) = 3, f (3) = 16
- 18. Using Cramer's law to solve the equation// 2x+5y=40 4x+8y=30
- 19. Using inverse matrix to solve linear equations, the first line X1 + 2x2 + 3x3 = 1, the second line 2x1 + 2x2 + 5x3 = 2, and the third line 3x1 + 5x2 + X3 = 3
- 20. How to find out the position of 0 element of vector in MATLAB