Newton's 2nd Law: Calculate Mass of Cart

[Igniuxx6]

Homework Statement

Influenced by certain force, cart moved from place and driven 0.5 meters distance. When 200grams weight was placed on cart it moved 0.3 meters during the same period of time. Calculate the mass of the cart.

 

[Daeho Ro]

So, how did you tried?

 

[Igniuxx6]

Tried to get acceleration by converting grams to kilos, then dividing 0,3 meters with 0,2 kilos. Got 1,5, but I doubt its right. If 1,5 would be correct, I would just use ΣF⃗=ma⃗

 

[Daeho Ro]

Then, why do you need the acceleration? I know you want to use the Newton's second law, but there are many missing parameters to use this.

 

[Igniuxx6]

I want acceleration to get force and with Force + Acceleration I would get mass. So what I should use instead? Pretty lost,

 

[Daeho Ro]

cart moved from place and driven 0.5 meters distance. When 200grams weight was placed on cart it moved 0.3 meters during the same period of time.

In this statement, I can get the velocity of cart and cart + 200grams weight, roughly. But I don't know how to get the acceleration.

 

[Igniuxx6]

How about _{a1=V1-V01/t a2=V2-V02/t} that leads to (V1-V01)*t/t*(V2-V02), we cancel out _t and we get (V1-V01)/(V2-V02), now I need to know how you get velocity of cart and cart + 200grams.

 

[ehild]

Tried to get acceleration by converting grams to kilos, then dividing 0,3 meters with 0,2 kilos. Got 1,5, but I doubt its right. If 1,5 would be correct, I would just use ΣF⃗=ma⃗

You know the displacements. Assuming uniform acceleration, how is the displacement related to time and the acceleration?

 

[Igniuxx6]

Displacement moves same distance each time interval

 

[Daeho Ro]

Displacement moves same distance each time interval

What you means is the constant velocity. Is this problem settle down with constant acceleration or constant velocity?

 

[Igniuxx6]

You mentioned you are abble to get velocity, if you would tell me how, I (maybe) would be abble to get acceleration from there and use it to get mass.

 

[Daeho Ro]

I supposed the cart moves without acceleration, that is constant velocity. Since we know the displacement within unknown time interval $T$, I can only tell you that the velocity is in a form $0.5 m / T$.

 

[ehild]

I supposed the cart moves without acceleration, that is constant velocity.

The problem statement is:

Influenced by certain force, cart moved from place and driven 0.5 meters distance.

If a certain force takes place, the velocity is not constant.

 

[Daeho Ro]

Influenced by certain force, cart moved from place and driven 0.5 meters distance.

If a certain force takes place, the velocity is not constant.

I thought the certain force only acted at the initial and the cart moves freely. But, it seems you are right. My poor English sometimes confuse me.

 

[Daeho Ro]

Ok, then now I am clear.

The cart with mass $M$ and cart + weight with mass $M + m$ moved by a fixed certain force $F$ and the displacements are $d_1$ and $d_2$, respectively.

 

[ehild]

That is true now.
But this is Igniuxx6's thread. Do not confuse him, and do not try to solve his problem. Both are against the rules of these Forums.

 

[Igniuxx6]

So
m2=0,2kg
m=m1+m2
F=d1+d2/m2=0,5+0,3/0,2=4N
a=F/m2=20
m1=F/a=4/20=0,2kg
m=0,2+0,2=0,4kg

 

[Daeho Ro]

In constant acceleration, the displacement is well known and because we know the displacement, you can get the acceleration.

F=d1+d2/m2=0,5+0,3/0,2=4N

This part is really strange. Why don't you check the relevant equations?

 

[Igniuxx6]

So its like a=9,8?
So it would be :
F=m*a=0,2*9,8=1,96N
m1=F/a=1,96/9,8=0,2kg
m=0,2+0,2=0,4kg?

 

[Daeho Ro]

For example, the displacement with constant velocity is given by $d = v t.$ What about the displacement with constant acceleration?

 

[Igniuxx6]

d = at? or d = 1/2at^2