Finding ratio of 2 masses with acceleration

[unoriginal]

Homework Statement

A force F applied to an object of mass m1 produces an acceleration of 3.00 m/s2. The same force applied to a second object of mass m2 produces an acceleration of 1.30 m/s2.

Find the ration of m1/m2

If m1 and m2 are combined, find their acceleration under the action of the force F.

Homework Equations

F=ma

The Attempt at a Solution

for the first part i just used F=m1x3 and F=m2x1.3 and put them together like m1x3=m2x1.3 and used 3/1.3 but that didnt work

 

[shadowtracker]

it would be 1.3/3 no 3/1.3 because if you have m1(3)=m2(1.3) then you divide by m2 and have m1(3)/m2=1.3 then divide by 3 and get m1/m2=1.3/3

 

[unoriginal]

ah stupid mistake on my part, got any ideas on the second part?

 

[sArGe99]

F = m1 a1
F = m2 a2

F/a1 = m1 and F/a2 = m2

F = (m1 + m2) x, x be the acceleration of the combined mass
x = F / (m1 + m2)

x = F / (F/a1 + F/a2)

x = 1 / (1/a1 + 1/a2)

x = a1.a2 / (a1 + a2)