# Momentum and movement basic GCSE Quest

• nonthesecond
In summary, when Mr Green, with a mass of 80 kg, stepped off a boat with a mass of 35 kg at a speed of 3m/s, the boat moved in the opposite direction at a speed of 240/35 m/s. The key concept to understand is that momentum is conserved in this scenario, meaning that the total momentum before and after Mr Green stepped off the boat should be equal to zero.
nonthesecond
Mr Green, mass 80 kg, stepped off a boat of mass 35 kg at a speed of 3m/s. how fast did the boat move in the opposite direction?

i have no idea how to work it out?

nonthesecond said:
Mr Green, mass 80 kg, stepped off a boat of mass 35 kg at a speed of 3m/s. how fast did the boat move in the opposite direction?

i have no idea how to work it out?

I think you will find that Mr Green and the boat are assumed to be at rest initially, so the total momentum was - and will remain - zero.

PeterO said:
I think you will find that Mr Green and the boat are assumed to be at rest initially, so the total momentum was - and will remain - zero.

ok thanks but how do i answer the question?

PeterO said:
I think you will find that Mr Green and the boat are assumed to be at rest initially, so the total momentum was - and will remain - zero.

i still don't understand i don't understand what formula to use as well.

nonthesecond said:
i still don't understand i don't understand what formula to use as well.

If you define the direction Mr Green goes as positive, he will have some positive momentum after he leaves the boat.
To maintain a total of zero, the boat must have an equal sized, but negative momentum - so it will be traveling at an appropriate speed in the negative direction (ie the other way)

PeterO said:
If you define the direction Mr Green goes as positive, he will have some positive momentum after he leaves the boat.
To maintain a total of zero, the boat must have an equal sized, but negative momentum - so it will be traveling at an appropriate speed in the negative direction (ie the other way)

i think i remeber my teacher saying that it's: 80 + 35= 115
115 x 3 = 375
375/35 = 1.3...m/s

is that correct?

nonthesecond said:
i think i remeber my teacher saying that it's: 80 + 35= 115
115 x 3 = 375
375/35 = 1.3...m/s

is that correct?

When you added the masses and multiplied by 3 (presumably the speed of Mr Green), you calculate the momentum if both he and the boat were traveling at that veocity; only he is.

nonthesecond said:
i think i remeber my teacher saying that it's: 80 + 35= 115
115 x 3 = 375
375/35 = 1.3...m/s

is that correct?

What is Mr Green's mass?

What is Mr Green's velocity?

What is Mr Green's momentum?

What is the boat's momentum?

What is the boat's mass?

What is the boat's velocity?

PeterO said:
What is Mr Green's mass?

What is Mr Green's velocity?

What is Mr Green's momentum?

What is the boat's momentum?

What is the boat's mass?

What is the boat's velocity?

you are very kind for helping me.

80kg

240 kg m/s

105 kg m/s

35kg

no idea for velocity i know formula is f=d/t but you aren't given time or distance.

nonthesecond said:
you are very kind for helping me.

80kg correct

(+3) - but you didn't answer that question

+240 kg m/s almost correct

105 kg m/s incorrect

35kg correct

no idea for velocity i know formula is f=d/t but you aren't given time or distance.

For that final velocity - think about how you calculated the momentum of Mr Green - and don't forget to use + and - signs correctly.
Velocity is a vector; so can be positive or negative.

PeterO said:
For that final velocity - think about how you calculated the momentum of Mr Green - and don't forget to use + and - signs correctly.
Velocity is a vector; so can be positive or negative.

PeterO said:
For that final velocity - think about how you calculated the momentum of Mr Green - and don't forget to use + and - signs correctly.
Velocity is a vector; so can be positive or negative.

did i get the question right?

nonthesecond said:

Certainly is.

## 1. What is momentum?

Momentum is a physics concept that describes the quantity of motion of an object. It is the product of an object's mass and its velocity.

## 2. How is momentum calculated?

Momentum is calculated by multiplying an object's mass (m) by its velocity (v), using the formula p = mv.

## 3. What is the law of conservation of momentum?

The law of conservation of momentum states that in a closed system, the total momentum of all objects before a collision is equal to the total momentum after the collision. This means that momentum is conserved and cannot be created or destroyed.

## 4. How does momentum affect movement?

Momentum affects movement by determining how much force is needed to change an object's motion. Objects with a larger momentum require more force to change their direction or speed compared to objects with a smaller momentum.

## 5. How is momentum related to inertia?

Momentum and inertia are closely related concepts. Inertia is the tendency of an object to resist changes in its motion, while momentum is the measure of an object's motion. Objects with a larger momentum have a greater resistance to changes in their motion due to their larger inertia.

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