IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: T.Q on November 21, 2009, 07:11:02 pm

Title: need help with this M1 question
Post by: T.Q on November 21, 2009, 07:11:02 pm

A competitor makes a dive from a high springboard into a diving pool. She leaves the
springboard vertically with a speed of 4 m/s upwards. When she leaves the springboard, she
is 5 m above the surface of the pool. The diver is modelled as a particle moving vertically under
gravity alone and it is assumed that she does not hit the springboard as she descends. Find
(a) her speed when she reaches the surface of the pool,

(b) the time taken to reach the surface of the pool.

(c) State two physical factors which have been ignored in the model.

i need help in part (B)

Title: Re: need help with this M1 question
Post by: astarmathsandphysics on November 21, 2009, 07:50:44 pm

Gimme 1 hour to get to c pc

Title: Re: need help with this M1 question
Post by: astarmathsandphysics on November 21, 2009, 10:03:03 pm

s=-5
u=4
v=
a=-9.8
t=
s=ut+1/2at^2
-5=4t-4.9t^2
4.9t^2-4t-5=0
use the quadratic formula to get t=1.5 or -/68 s
but t is positive therefore t=1.5seconds

Title: Re: need help with this M1 question
Post by: T.Q on November 21, 2009, 10:24:38 pm

Quote from: astarmathsandphysics on November 21, 2009, 10:03:03 pm

s=-5
u=4
v=
a=-9.8
t=
s=ut+1/2at^2
-5=4t-4.9t^2
4.9t^2-4t-5=0
use the quadratic formula to get t=1.5 or -/68 s
but t is positive therefore t=1.5seconds

thank you