# Momentum Change of Colliding Balls: A Physics Problem

• Count Duckula
In summary, the conversation discusses a physics problem involving two balls colliding with each other. The question is to find the momentum and velocity of both balls after the collision. The person is unsure of which equation to use and asks for clarification. The expert explains that the resultant force on both balls is zero due to conservation of momentum and provides a hint on how to solve the problem.

#### Count Duckula

ok so my physics textbooks crap, it explains something in a tiny paragraph without any examples (I'm getting new ones). I have this question I'm stuck on. There is 2 balls that both have the mass of 1.5kg, one is not moving and one is moving at 4m/s - so ball A is about to collide with ball B. the questions are: the momentum of ball A just after collision, momentum of ball B just after collision and velocity of ball B after the collision?

do I use force= change in momentum/time taken for the change equation. so for the first two I am guessing the question is to find the change in momentum which is force x time taken for change. but what is the time taken for the change - is it 4m/s? or do I need a different equation to find out the time it took for the change and then use that to find out the change in momentum?

What is the resultant force on BOTH balls when they collide with each other?

grzz said:
What is the resultant force on BOTH balls when they collide with each other?

I don't know, all the information for the question I have is what I have given...

... oh... under the question there's another line that says, 'after the collision both balls move to the right but the velocity of ball A is now 1m/s

... I should be able to figure out these questions now, I think... maybe if you could do the first for me? so I have something to work from, as I have no example to get an idea with.

when the two balls collide with each other, ball A gives a force to ball B and ball B gives an equal and opposite force to ball A. Hence the resultant force on the two balls taken together is zero.

Hence momentum is conserved.

i.e. initial momentum = final momentum.

Try to work out this equation and you get the answer required.

I would approach this problem by first understanding the concept of momentum and how it relates to collisions. Momentum is a property of an object that describes its motion and is calculated by multiplying its mass by its velocity. In a collision, the total momentum of the system (both balls) is conserved, meaning it remains the same before and after the collision.

To answer the first question, we can use the equation for conservation of momentum: m1v1 + m2v2 = m1v1' + m2v2', where m represents mass and v represents velocity before and after the collision, respectively. In this case, ball A is not moving before the collision, so its momentum is 0. Ball B has a mass of 1.5kg and a velocity of 4m/s, so its momentum before the collision is 1.5kg*4m/s = 6kgm/s. After the collision, both balls will be moving together with a shared velocity, so we can rewrite the equation as (m1+m2)v' = m1v1 + m2v2. Plugging in the values, we get (1.5kg+1.5kg)v' = 1.5kg*0m/s + 1.5kg*4m/s, giving us a final velocity of 4m/s for both balls after the collision.

To answer the second question, we can use the same equation and plug in the values for ball A and the final velocity we just calculated for ball B. This will give us a momentum of 6kgm/s for ball A after the collision.

For the third question, we can use the equation for conservation of energy: 1/2mv^2 = KE, where m represents mass, v represents velocity, and KE represents kinetic energy. Since we know the mass and velocity of ball B after the collision, we can calculate its kinetic energy. Then, using the equation KE = 1/2mv^2, we can solve for v to find the final velocity of ball B after the collision.

In summary, to solve this problem, we used the principles of conservation of momentum and energy to calculate the momentum and velocity of both balls after the collision. It is important to understand and apply these concepts in order to solve physics problems accurately. I would also recommend referring to a more comprehensive textbook or consulting with a teacher or tutor to gain a

## 1. What is momentum change?

Momentum change is a physics concept that refers to the change in the amount of motion an object has. It is calculated by multiplying an object's mass by its velocity.

## 2. How is momentum change related to colliding balls?

When two balls collide, they exert a force on each other that causes a change in their individual momentums. This change in momentum can be calculated using the law of conservation of momentum, which states that the total momentum of a closed system remains constant.

## 3. Is the momentum change the same for both colliding balls?

According to the law of conservation of momentum, the total momentum of the colliding balls before and after the collision remains the same. However, the individual momentum change for each ball may be different depending on factors such as mass and velocity.

## 4. How can momentum change be calculated for colliding balls?

Momentum change for colliding balls can be calculated using the formula Δp = mΔv, where Δp is the change in momentum, m is the mass of the ball, and Δv is the change in velocity.

## 5. What factors affect the momentum change of colliding balls?

The momentum change of colliding balls is affected by factors such as the mass and velocity of the balls, the angle and speed of collision, and the elasticity of the balls. These factors can impact the amount of force exerted and the resulting change in momentum.