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

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To determine the work required to stop a car weighing 5490 N before a collapsed bridge, the mass can be calculated using the equation F = ma, where the weight (force due to gravity) is given. The deceleration of the car is -10.9 m/s², which can be used to find the frictional force acting on the car. Once the frictional force is known, the work done can be calculated using the formula Work = Force x Distance. The distance to the bridge is 29.3 m, which is crucial for calculating the total work needed to stop the car in time.
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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?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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