college physics
posted by john .
Superman must stop a 190km/h train in 180m to keep it from hitting a stalled car on the tracks.
part a)If the train's mass is 3.8×10^5kg , how much force must he exert (find the magnitude)?
part b)Compare to the weight of the train (give as %).
partc) How much force(in magnitude) does the train exert on Superman?

(a) v=190 km/h =52.8 m/s,
a =v^2/2•s =(52.8)^2/2•180 = 7.74 m/s^2,
F = m•a = 3.8•10^5•7.74 = 2.94•10^6 N.
(b) Weight = mg = 3.8•10^5•9.8= 3.76•10^6 N.
(c) F12 = F21 = >
F = 2.94•10^6 N. 
for part b, what would be the percentage. i got 10% but it isnt right

John: show your work, you wouldn't want anyone to think you are answer grazing.
percent= force/mass*g * 100 
i got it its 79% i was label some of the numbers with the wrong variables. tahnks and will keep that in mind
Respond to this Question
Similar Questions

physics
Find the speed at which Superman (mass=89.0 kg) must fly into a train (mass = 19564 kg) traveling at 65.0 km/hr to stop it. The system (train + Superman) must end up with zero momentum. With no external forces, Superman's initial momentum … 
physics
need help on this three part one its about inelastic collisions momentum and energy related with work Find the speed at which Superman (mass=76.0 kg) must fly into a train (mass = 17620 kg) traveling at 60.0 km/hr to stop it. Running … 
Physics
Find the speed at which Superman (mass=88.0 kg) must fly into a train (mass = 17998 kg) traveling at 60.0 km/hr to stop it. Running into the train at that speed would severely damage both train and passengers. Calculate the minimum … 
Physics
Find the speed at which Superman (mass=88.0 kg) must fly into a train (mass = 17998 kg) traveling at 60.0 km/hr to stop it. Running into the train at that speed would severely damage both train and passengers. Calculate the minimum … 
physic
Superman must stop a 120km/h train in 150m to keep it from hitting a stalled car on the tracks.If the train's mass is 3.6x10^5kg,how much force must he exert? 
physic
Superman must stop a 120km/h train in 150m to keep it from hitting a stalled car on the tracks.If the train's mass is 3.6x10^5kg,how much force must he exert? 
@elena
thank you so much help with the problem. i have trouble solving part b of the problem you helped me with. it told me to give it as a percentage, I got 10% but it is wrong. can you please help me Superman must stop a 190km/h train … 
Physics
As a train approaches the city it sees a stalled car on the tracks. The train slams on its brakes going from 25 m/s to rest in 30 s. How far away was the stalled car when the train conductor slammed on the brakes? 
physics
Superman must stop a 120km/h train in 150m to keep it from hitting a stalled car on the tracks.If the train's mass is 3.6x10^5kg,how much force must he exert? 
physics
Superman must stop a 110km/h train in 100m to keep it from hitting a stalled car on the tracks. The train's mass is 3.6 × 105 kg.