Homework in physics (average force and momentum)

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Homework Help Overview

The discussion revolves around a physics problem involving a car's collision with a tree, focusing on concepts of momentum and average force. The original poster presents a scenario where a 1000 kg car strikes a tree at a speed of 30 km/hr and comes to a stop in 0.15 seconds, seeking assistance in calculating the initial momentum and average force during the stop.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to convert the car's speed from km/hr to m/s and calculates the momentum using the formula p = mv. They express uncertainty about the correctness of their calculations and seek guidance on finding the average force. Other participants suggest considering the impulse delivered by the tree and refer to the impulse-momentum theorem, prompting further inquiry into its definition and application.

Discussion Status

The discussion is ongoing, with participants providing hints and references to relevant concepts without reaching a consensus. The original poster has received confirmation on their momentum calculation but is still exploring how to apply the impulse-momentum theorem to find the average force.

Contextual Notes

The original poster notes that they are limited to the mass, velocity, and time provided in the problem, indicating constraints on the information available for solving the average force.

yek_zzz
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Homework Statement

A 1000 kg car strikes a tree at 30 km/hr & comes to a stop in 0.15s. Find its initial momentum and the average force on the car while it is being stopped.


Attempt at a solution

For velocity,

I tried converting 30 km/hr to m/s

30 km/hr * 1hr/3600s*1000m/1km

=30000 m/ 3600 s = 8.33 m/s

For the momentum...

p = mv

p = 1000 kg (8.33 m/s)

p = 8330 kg * m/s

Is this correct? How do I find the average force? Please help me. My teacher says I'm wrong at some equation.
 
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Everything you've done so far is correct. To find the average force, consider the impulse delivered by the tree.
 
how do I solve for that? We are only given the mass, velocity and the time.
 
You have all you need. What's the definition of impulse? Look up the impulse-momentum theorem. You'll set up an equation and solve for the force.
 

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