How Much Work is Required to Stop a Car Just Before a Collapsed Bridge?

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SUMMARY

The discussion focuses on calculating the work required to stop a car weighing 5490 N before a collapsed bridge, with a constant deceleration of 10.9 m/s². To find the mass of the car, the weight (5490 N) is divided by the acceleration due to gravity (9.8 m/s²), resulting in a mass of approximately 560 kg. The work done to stop the car can be calculated using the formula for kinetic energy (KE = 1/2mv²) and the frictional force derived from the deceleration. The final answer is expressed in joules (J).

PREREQUISITES
  • Understanding of Newton's second law (F = ma)
  • Knowledge of kinetic energy formula (KE = 1/2mv²)
  • Familiarity with gravitational force calculations (FN = mg)
  • Basic concepts of friction and deceleration
NEXT STEPS
  • Calculate the mass of an object from its weight using the formula m = weight/g
  • Explore the relationship between frictional force and deceleration
  • Learn how to calculate work done using the formula W = Fd
  • Investigate real-world applications of stopping distances in vehicle safety
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Students studying physics, particularly those focusing on mechanics and forces, as well as educators looking for practical examples of work and energy concepts.

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Homework Statement


A car and driver weighing 5490 N passes a sign stating “Bridge Out 29.3 m Ahead.”
She slams on the brakes, and the car decelerates at a constant rate of 10.9 m/s2.
The acceleration of gravity is 9.8 m/s2 .
What is the magnitude of the work done stopping the car if the car just stops in time to avoid diving into the water?
Answer in units of J.


Homework Equations


KE = 1/2mv^2
Ff = u * FN
FN = mg
F = ma


The Attempt at a Solution


Given:
a = -10.9
Fg = 9.8

need help in setting this problem up... I've never seen something weigh in N before is that important or relevant in any way? would I plug that into F = ma to find mass?
help please!
 
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If the weight is 5490 N, can you find the mass of the person+car ?

If the deceleration is -10.9 m/s2 , can you get the force of friction acting on the car?

If you have the frictional force, can you find the work done by this force given the distance?
 

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