The law of conservation of momentum says that the total momentum in the system before and after the collision remains the same. Remember that <em>p = mv </em>(where p is momentum, m is mass, and v is velocity). To find the total momentum in the system, add up the momentum of each component.
Before the collision:
The momentum of the first cart is m*v = 1.5 * 1.2 = 1.8.
The momentum of the second cart is m*v = 0.75 * 0 = 0.
The total momentum is 1.8.
After the collision:
(where x is the unknown velocity):
The momentum of the first cart is m*v = 1.5x
The momentum of the second card is m*v = 0.75 * 2 = 1.5.
The total momentum is 1.5x + 1.5. Because of conservation of momentum, you know this is equal to the momentum before the collision:
1.8 = 1.5x + 1.5
Subtracting 1.5 from both sides:
0.3 = 1.5x
And dividing by 1.5:
x = 0.2 m/s forward (you know it is forward because it is positive)
Answer:
a) v = 7,207 m / s
, b) a = 42.3 m / s²
Explanation:
We will solve this exercise using the concept of mechanical energy, We will write it in two points before the car touches the springs and in point of maximum compression
Initial
Em₀ = K = ½ m v²
Final
= 2 Ke = ½ k x²
The two is placed because each barred has two springs and each does not exert the same force
Emo = 
½ m v² = 2 ½ k x²
v = √(2k/m) x
v = √ (2 3,134 10⁵/4550) 0.614
v = 7,207 m / s
Let's take this speed to km / h
v = 5,096 m / s (1km / 1000m) (3600s / 1h)
v = 25.9 km / h
This speed is common in school zones
Let's use kinematics to calculate the average acceleration
vf² = v₀² - 2 a x
0 = v₀² - 2 a x
a = v₀² / 2 x
a = 7,207²/2 0.614
a = 42.3 m / s²
We buy this acceleration with the acceleration of gravity
a / g = 42.3 / 9.8
a / g = 4.3
This acceleration is well below the maximum allowed