(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Hi

I have been stumped by this question for the past few days. Worrying since I will be sitting STEP in June! Never mind. It goes like this:

A particle is projected vertically upwards with a speed of 30m/s from a point A. The point B is h metres above A. The particle moves freely under gravity and is above B for a time 2.4s. Calculate the value of h.

2. Relevant equations

V=U + at

V^2=U^s +2aS

3. The attempt at a solution

These are my parameters:

From A to B

u=30

a=-9.8

s=h

From B

u=?

a=-9.8

s=?

t=2.4

I took t=2.4 as the Maximum height above B.(I am not sure about this line of reasoning!)

Based on that V=0

Using V=U + at

U=23.52 m/s (This seemed to make sense since particle will start decelerating at some point)

So, U (at b)=23.52 m/s

Considering it from A to B

U=30

V=23.52

a=-9.8

S=h

Using V^2=U^s +2aS

h=17.7m (3s.f)

But alas, it seems my answer (and probable reasoning) is wrong. Any suggestions???

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# Projected particle

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