Homework Help: physics- pls help me

Posted by Dora on Wednesday, October 7, 2009 at 5:05pm.

1. The driver of a car slams on the brakes when he sees a tree blocking the road. The car slows uniformly with acceleration -5.20 m/s2 for 4.45 s, making straight skid marks 62.5 m long ending at the tree. With what speed does the car then strike the tree?

2. A jet plane lands with a speed of 80.0 m/s and can accelerate with a maximum magnitude of 7.00 m/s2 as it comes to rest.

(a) From the instant the plane touches the runway, what is the minimum time interval needed before it can come to rest?

(b) Can this plane land on a small tropical island airport where the runway is 0.800 km long?

yes or no

(c) What is the minimum distance the plane requires to land? (in km)

physics- pls help me - bobpursley, Wednesday, October 7, 2009 at 5:32pm
1. You know the distance. Find the terminal velocity.

Vf^2=Vo^2-2ad

2. Nuts to the problem statement. Planes have to deaccelerate to stop.

Vf=Vo-a*t solve for time t.
distance=Vo*tmin -1/2 a tmin^2

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