Basic linear motion question.Is it good?

[german1234]

Homework Statement

Airport runway designing:

(i)lowest acceleration rate of any plane is likely to be 3m/s^2.Take off speed for this airplane will be 65m/s.what is minimum allowed length of runway?

(ii)If airplane accelerates down runway at 3.2m/s^ for 32.8 seconds until it lifts off..determine distance traveled before take-off.

(iii)Another airplane has take off speed of 88.3m/s and needs 1365m to reach this speed.determine acceleration of plane and time taken to reach this speed.

Homework Equations

v=u+at

v^2=u^2+2as

s=ut+(1/2)at^2

The Attempt at a Solution

(i) a=3
u=0
v=65
s=? v^2=u^2+2as

65^2=0^2+2(3)s
4225=6s
s=4225/3
s= 704.2 m

(ii) a=3.2
t=32.8
u=0
s=?
s=ut+(1/2)at^2

s=0(32.8)+(1/2)(3.2)(32.8)^2

s=1721.3m

(iii)v=88.3
u=0
s=1365
t=?

v^2=u^2+2as

(88.3)^2=0^2+2a(1365)

7796.89=2730a

a=2.856m/s^2

Now:
v=u+at

88.3=0+2.856(t)

t=30.9 seconds

Thanks in advance

 

[collinsmark]

'Looks okay to me.