Homework Help: college physics

Posted by john on Sunday, April 29, 2012 at 4:59pm.

Superman must stop a 190-km/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?

college physics - Elena, Sunday, April 29, 2012 at 5:09pm
(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.
@elena Question ! - john, Sunday, April 29, 2012 at 5:45pm
for part b, what would be the percentage. i got 10% but it isnt right
college physics - bobpursley, Sunday, April 29, 2012 at 5:50pm
John: show your work, you wouldn't want anyone to think you are answer grazing.

percent= force/mass*g * 100
college physics - john, Sunday, April 29, 2012 at 5:55pm
i got it its 79% i was label some of the numbers with the wrong variables. tahnks and will keep that in mind

Answer this Question

Related Questions

@elena - thank you so much help with the problem. i have trouble solving part b ...
physic - Superman must stop a 120km/h train in 150m to keep it from hitting a ...
physic - Superman must stop a 120km/h train in 150m to keep it from hitting a ...
physics - Find the speed at which Superman (mass=89.0 kg) must fly into a train...
Physics - Find the speed at which Superman (mass=88.0 kg) must fly into a train...
Physics - Find the speed at which Superman (mass=88.0 kg) must fly into a train...
physics - need help on this three part one its about inelastic collisions ...
physics - Running into the train at that speed would severely damage both train ...
physics - The last car unfastens from a moving train. The train continues to ...
physics - A red train traveling at 72 km/h and a green train traveling at 144 ...

For Further Reading

First Name:
School Subject:
Answer: