These skaters are racing each other at Newton’s Skate Park. The first skater in line loses focus on her task. She starts to slow down without realizing it. The skater behind her isn’t paying attention and keeps skating at the same
.
::这些滑冰者在牛顿滑雪公园相互赛跑。 第一位滑冰者对她的任务失去关注。 她开始放慢速度而没有意识到这一点。 她身后的滑冰者没有注意,并一直在同一时间滑冰。
Q
: Can you guess what happens next?
::问:你能猜到接下来会发生什么吗?
A
: Skater 2 runs into skater 1.
::A:Skater 2号撞向滑板1号。
Conserving Momentum
::保护动力
(
p
) is a property of a moving object that makes it hard to stop. It’s a product of the object’s mass (
m
) and
, this is written as the following equation:
:p) 是移动对象的属性,使其难以停止。它是物体质量(m)的产物。
::p=mv =p=mv =pp =mv =pmv =pp=mv =pmv
Skater 2, who has more momentum than skater 1, collides with skater 1. At the moment of the collision, skater 2 transfers some of her momentum to skater 1, who shoots forward when skater 2 runs into her. Whenever an action and reaction such as this occur, momentum is transferred from one object to the other. However, the combined momentum of the objects remains the same. In other words, momentum is conserved. This is the
law of conservation of momentum
.
::1. 在碰撞发生时,滑冰者2号将她的一些动力转移到滑冰者1号,当滑冰者2号进入她身旁时,他向前射击。每当出现这种行动和反应时,动力从一个物体转移到另一个物体,但物体的综合动力保持不变。换句话说,保持势头。这就是保持势头的法律。
Watch the video below to learn more:
::观看下面的视频以学习更多:
Modeling Momentum
::建模动力
The
Figure
shows how momentum is conserved in the two colliding skaters, both travelling in the same direction. Skater 1 has a mass of 80 kg and is moving at 1 m/s before the collision. Skater 2 has a mass of 70 kg and has a velocity of 2m/s before the collision. After the collision, skater 1 has a velocity of 1.7 m/s and skater 2 has a velocity of 1.2 m/s. The total momentum is the same after the collision as it was before. However, after the collision, skater 1 has more momentum and skater 2 has less momentum than before.
::图中显示了两个相撞的滑冰者如何保持势头,它们都朝同一方向飞行。Skater 1号的重量为80公斤,在碰撞前以每秒1米的速度移动。Skater 2号的重量为70公斤,在碰撞前速度为每秒2米。碰撞后,Skater 1号的速率为1.7米/秒,滑冰者2号的速率为1.2米/秒。在碰撞后,总的势头与以前相同。然而,碰撞后,滑冰者1号的速率比以前高,滑冰者2号的速率比以前低。
Data table for
Figure
Momentum
before
the collision
Momentum
after
the collision
Skater 1
p
1
= 80 kg × 1 m/s
::p1 = 80公斤x 1米/秒
p
1
= 80 kg m/s
::p1 = 80公斤米/秒
p
1
= 80 kg × 1.7 m/s
::p1 = 80公斤x 1.7米/秒
p
1
= 136 kg m/s
::p1 = 136公斤米/秒
Skater 2
p
2
= 70 kg × 2 m/s
::p2 = 70公斤× 2米/秒
p
2
= 140 kg m/s
::p2 = 140公斤米/秒
p
2
= 70 kg × 1.2 m/s
::p2=70公斤x1.2米/秒
p
2
= 84 kg m/s
::p2 = 84公斤米/秒
Total Momentum of Skater 1 and 2
p
total
= p
1
+ p
2
::总计=p1+p2
p
total
= 80 kg m/s + 140 kg m/s
::总计=80公斤/秒+140公斤/秒
p
total
= 220 kg m/s
::总计=220公斤米/秒
p
total
= p
1
+ p
2
::总计=p1+p2
p
total
= 136 kg m/s + 84 kg m/s
::合计=136公斤/秒+84公斤/秒
p
total
= 220 kg m/s
::总计=220公斤米/秒
The total momentum is the same after the collision is the same as before. However, skater 1 has more momentum after the collision, and skater 2 has less momentum than before.
::但是,滑冰者一号在碰撞后势头更大,滑冰者二号比以前的势头更少。
Q
: What if two skaters have a head-on collision? Do you think momentum is conserved then?
::问:如果两个滑冰者正面碰撞呢?你认为势头节制了吗?
A
: As in all actions and reactions, momentum is also conserved in a head-on collision.
::A:与所有行动和反应一样,正面碰撞也保持了势头。
Summary
::摘要
Whenever an action and reaction occur, momentum is transferred from one object to the other. However, total momentum is conserved. This is the law of conservation of momentum.
::每当出现行动和反应时,动力就会从一个物体转移到另一个物体,但总势头会得到保持,这是保持势头的法律。
Review
::回顾
State the law of conservation of momentum.
::国家保持势头法。
Fill in the missing velocity (x) in the diagram of a vehicle collision seen in the
Figure
so that momentum is conserved.
::填充图中车辆碰撞图中缺失的速度(x),以保持势头。
p) 是移动对象的属性,使其难以停止。它是物体质量(m)的产物。
