Motion Question: Calculating Change in Momentum and Resultant Force

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Homework Help Overview

The discussion revolves around a physics problem involving the calculation of change in momentum and resultant force for a lorry with a specified mass and change in velocity over a given time period.

Discussion Character

  • Mixed

Approaches and Questions Raised

  • The original poster attempts to calculate the change in momentum using the formula for momentum but expresses uncertainty regarding the calculation of the average resultant force. Some participants suggest looking up the impulse-momentum theorem and discuss its application to the problem.

Discussion Status

Participants are exploring the relationship between impulse and momentum, with some guidance offered regarding the impulse-momentum theorem. There is an ongoing clarification of the formulas involved, but no consensus has been reached on the final approach to solving part b of the problem.

Contextual Notes

The problem includes specific values for mass, initial and final velocities, and a time duration for the change, but the original poster has not fully resolved the application of these values to find the resultant force.

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Homework Statement


A lorry of a mass 1500kg increases its velocity from 12m/s to 20m/s.

Homework Equations


a) calculate the change in momentum of the lorry.
b) The time taken for this change in velocity id 2 minutes. Calculate the average resultant force applied on the lorry.

The Attempt at a Solution


I worked out part a) by using the formula momentum= mv and got the ans 12000kgm/s
but i don't know how to work out part b.
Does anyone know how ?
 
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Look up the impulse-momentum theorem.
 
Thank you so the formula is that ? F⃗ Δt=Δp⃗ =m(v⃗ f−v⃗ i)
So the Force= mass (velocity * f orce - velocity* impulse)?
 
MsTech said:
Thank you so the formula is that ? F⃗ Δt=Δp⃗ =m(v⃗ f−v⃗ i)
So the Force= mass (velocity * f orce - velocity* impulse)?
Not exactly. Impulse = FΔt. The impulse momentum theorem states that the impulse will equal the change in momentum:

FΔt = Δ(mv) = m Δv
 
Ah i tought it didn't make sense ! Ok got it ! thanks a lot :-)
 

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