Calculate the mass of a trolley

[jamesd2008]

Hi every body hope you can help. I have been set a problem to solve the mass of a trolley. The trolley is sat on an air track, attached is a string which is lead over a pulley and has a mass attached at the end hanging over the edge. The mass at the end has 1.4 meters to fall and does it in 3.4 sec, hence moving the trolley along the air track.

Mass of the weight is 10 grams
Mass of the pulley is 34 grams and has a diameter of 49mm
Distance above ground is 1.4m and the time taken is 3.4secs

I know this is an energy problem i.e P.E goes to K.E and i think the Inertia (I) of the pulley is I=mr^2. Were m is the mass of the pulley and r is the radius of the pulley.

At the start I've got the potential energy of the weight but after that I'm stuck and can't figure out how to calculate the mass of the trolley. Hope someone can help every time i do it the mass of the trolley ends up at like 2700grams which i know is wrong.

Thanks in advance James

 

[Navin A S]

To solve this problem, you need to consider the conservation of energy. Since the gravitational potential energy of the weight decreases as it falls, that energy must be converted into another form (kinetic energy). The kinetic energy of the trolley is equal to the gravitational potential energy of the weight. Thus, the mass of the trolley can be calculated using the equation:KE = m*v^2/2where m is the mass of the trolley, and v is the velocity of the trolley after the weight has dropped. You know the distance and the time, so you can calculate the velocity of the trolley. Then, you can solve for the mass. Hope this helps!