Calculating Net Force and Deacceleration in a Head-On Collision

AI Thread Summary
In a head-on collision scenario involving a 58 kg person in a car traveling at 13 m/s, the net force on the person was calculated based on deceleration over a distance of 1 meter while wearing a seatbelt. The deceleration was found to be -84.5 m/s², leading to a calculated net force of -4901 N. However, the answer was marked incorrect, prompting a request for assistance in identifying the error. The discussion also touched on the potential movement of the person during the collision, suggesting that additional factors may need to be considered. Accurate calculations and attention to significant figures are emphasized as crucial for correct results.
Sky.Anthony
Messages
10
Reaction score
0

Homework Statement



A 58 kg person is in a head-on collision. The car's speed at impact is 13 m/s. Estimate the net force on the person if he or she is wearing a seat belt and if the air bag deploys.

For some reason, I can't seem to get the correct answer to this question... I have no idea where I am going wrong. According to the question, if a person is wearing a seatbelt, they deaccelerate over a distance of 1m.

Homework Equations



(Final Velocity)^2 = (Initial Velocity)^2 + 2*acceleration*distance
Force=mass*acceleration

The Attempt at a Solution



First off, I had to find the deacceleration over the distance of 1m:
(Final Velocity)^2 = (Initial Velocity)^2 + 2*acceleration*distance
0 = (13m/s)^2 + 2*acceleration*1m
acceleration= -84.5m/s^2

Using that acceleration to calculate net force...
F=ma
= (58kg)(-84.5m/s^2)
=-4901N

I put that answer into the system and it comes back wrong...

Help is appreciated. Thanks!
 
Physics news on Phys.org
well it sound reasonable to me
but thinking back if a person wearing seatbelt should they move forward then move back ward?
 
Don't forget about your significant figures.
 
I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
Thread 'A cylinder connected to a hanging mass'
Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
Back
Top