Help with a physics question!

x

Considering the forces acting on the body, you arrive at:

T-mg = ma

Then, just substitute the values you are given into the question

70 - 10m = 4m

70=14m

m = 70/14




Not sure on rules for posting solutions...but erm...yeah...

Best way of approaching this is to just consider the forces on the body that is hanging in the lift. The body itself only has two forces acting on it, the weight and the tension of the spring. We know the tension must be 70N as the question has told you the reading. You can use this information to get the resultant force on the body in terms of m. Using this you can work out the mass of the body with F=ma, as you also know the acceleration.

Hope this is useful