急!!!物理學問題!!!!〈盡快〉

1、a student throws a ball vertically upward such that it travels 7.1m to its maximum height. If the ball is caught at the initial height 2.4 s after being thrown,what is the ball's average speed,and what is its average velocity?

自己的翻譯〈不一定對〉：一位學生垂直地向上丟一個球到它的最大高度移動7.1m。如果球被拿到在最初的高度2.4s再被投擲以後，試問球的平均速度?平均速率?

2、two runners approaching each other on a straight track have constant speeds of 4.5m/s and 3.50m/s , respectively, when they are 100m apart. how long will it take for the runners to meet,and at what position will they meet if they maintain these speeds?

自己的翻譯〈不一定對〉：2個跑者在一條長100公尺的直線道路上分别以4.5m/s和3.50m/s的速度接近對方，試問他們要跑多久才會相遇?還有，如果他們維持這樣的速度那他們會在哪個位置相遇???

3、the driver of a pickup truck going 100km/h applies the brakes,giving the truck a uniform deceleration of 6.5m/s while it travels 20m.

what is the speed of the truck in kilometers per hour at the end of this distance? how much time has elapsed?

自己的翻譯〈不一定對〉：卡車原本時速100公里，當他移動20m之後，以6.5m/s的速度減速，試問在卡車完全停下來須花多少時間?〈另一個問題我不會翻，麻煩讀者請自行翻譯

4、a student drops a ball from the top of a tall building ; the ball takes 2.8s to reach the ground . what was the ball,s speed just before hitting the ground? what is the height of the building?

自己的翻譯〈不一定對〉：一個學生從一個高樓上面丟下球; 球以2.8s的速度到達地面。試問此大樓的高度為何?球在擊中地面之前的速度是多少?

5、you throw a stone vertically upward with an initial speed of 6m/s from a third-story office window.if the window is 12m above the ground,find the time the stone is in flight and the speed of the stone just before it hits the ground.

自己的翻譯〈不一定對〉：你在三樓窗口以6m/s的速度垂直向上丟一顆石頭，若窗口離地面12m，試問石頭的飛行時間是多少?在它落地前的速度是多少?

※請會的人盡快解題呦!!!!感激不盡!!!!!