[serenitymantra]

Two objects are in contact with each other on the floor. Object 1 has a mass 3x as big as object 2. If you push object 1 with a horizontal force, what net force will object 1 experience?

Any push in the right direction would be greatly appreciated. Thanks!

[Unknown008]

Use F=ma. When you push one, they'll have the same acceleration. Call the acceleration a, force F the total force being exerted, and m the total mass.

Say, the mass of the large one be 3x, and the mass of the smaller one be 2x.

Use F=ma again, using the acceleration a which is common in both cases. Substitute for their respective mass, and you'll have the force as a fraction of the total exerted force. This way, you'll have the fraction of the total force exerted on both bodies.

Tell me what you've got. These types of questions are quite frequent in examinations.

[serenitymantra]

Use F=ma. When you push one, they'll have the same acceleration. Call the acceleration a, force F the total force being exerted, and m the total mass.

Say, the mass of the large one be 3x, and the mass of the smaller one be 2x.

Use F=ma again, using the acceleration a which is common in both cases. Substitute for their respective mass, and you'll have the force as a fraction of the total exerted force. This way, you'll have the fraction of the total force exerted on both bodies.

Tell me what you've got. These types of questions are quite frequent in examinations.

What I tried was:
F=100, object 1: m= 3, object 2: m=1.
Object 1: I applied a force of 100 then divided it by the m=3 so I have a1= 33.33,
then for object 2 I applied the same force, but this time dividing it by m 1 and m2 because object 1 is pushing object 2, so it's a complete system.. and I got a2= 25. Comparing a1 and a2, I found that a1 is .75 of a2... 33.33X.75=25.

Does that sound right?

[Unknown008]

No, no no. You have to look at the system as a whole at the start. The total mass in your example is 3+1 = 4. So, the whole system accelerates by the same amount.

I'll take a visual example. Take a pencil and a book. Put the pencil before the book so that they are in contact and push the pencil towards the book. Both will speed up at the same rate.

So, here, total Force = 100N
Acceleration = F/m = 100/4 = 25 m/s^2

So, the force that is applied on object one = ma = 3*25 = 75 N
Force applied on object two = ma = 1*25 = 25 N

The forces are different, but acceleration are the same.

[serenitymantra]

No, no no. You have to look at the system as a whole at the start. The total mass in your example is 3+1 = 4. So, the whole system accelerates by the same amount.

I'll take a visual example. Take a pencil and a book. Put the pencil before the book so that they are in contact and push the pencil towards the book. Both will speed up at the same rate.

So, here, total Force = 100N
Acceleration = F/m = 100/4 = 25 m/s^2

So, the force that is applied on object one = ma = 3*25 = 75 N
Force applied on object two = ma = 1*25 = 25 N

The forces are different, but acceleration are the same.

After a few more trials, I did end up treating the system as whole. My thinking was, the object is box, so w/ obj 1 being 3x as big, if I push on obj 2 which I set to 1, obj 1 will experience 3/4 F because object 2 takes up 1/4 F.

[Unknown008]

Good! Seems you've understood! :)

[serenitymantra]

Thanks for the help!

[Unknown008]

You're most welcomed! :)