A vertical light rod PQ has a particle of mass 0.5 kg attached to it at P and a particle of mass 0.75 kg attached to it at Q, to form a system, as shown in Figure 2 - Edexcel - A-Level Maths Mechanics - Question 5 - 2017 - Paper 1

For the particle at P, the equation of motion gives:

$T - 0.5g = 0$

This means:

$T = 0.5g$

To find the acceleration of the system, we can combine the equations derived. From the equation for T:

$T = 15 - 0.75g$

Substituting $T$ from the second equation:

$15 - 0.75g = 0.5g$

Rearranging this gives:

$15 = 0.75g + 0.5g$ $15 = 1.25g$

action of gravity is approximately $9.8 ms^{-2}$: g = rac{15}{1.25} = 12 ms^{-2}

Now substituting the value of g back into one of the equations to find T, we use:

T = 4.9 N$$ The thrust in the rod is therefore: **Thrust, T = 6N**