Simple Pressure Ballet dancer Problem

[sun]

Homework Statement

A 50kg ballet dancer stands on her toes during a performance with four square inches (26cm^2) in contact with the floor. What is the pressure exerted by the floor over the area of contact? (a) if the dancer is stationary and (b) if the dancer leaps upwards with an acceleration of 4m/s^2?

Homework Equations

26cm^2=.26m^2
P=F/A
F=mg

The Attempt at a Solution

For question (a) i got the force to be 50(9.8)=490N, then i divided that by .26m^2. I keep getting an incorrect answer. what am i doing wrong? Also, are there any suggestions on how to set up part (b)?


I know the answers are: (a) 1.88X10^5Pa, (b)2.65X10^5Pa
thank you

 

[rock.freak667]

1cm^2=10^-4 m^2

 

[rl.bhat]

26cm^2=.26m^2. This is wrong.
26cm^2=26*10^-4m^2.
In part B force = 50*(9.8 + 4 ) N

 

[sun]

Thanks to both of you. What careless errors on my part. :(