Hanging Mass and Car Lab Write-Up

How do the predicted velocity and the measured velocity compare in each case?  Did your measurements agree with your initial prediction?  If not, why? 

When mass weights varied, the velocities were slightly off, with around a 7-8% difference. When the distance varied, the velocities were fairly close, with around a 1% difference, but some were off by around an 8% difference. When the car weight varied, some velocities were close with around a 1% difference, but others were off by 8%. Most of the measurements agreed with the initial prediction. Some values were most likely different due to human error and environmental factors when we released the car and while performing video analysis.

Does the launch velocity of the car depend on its mass?  The mass of the block?  The distance the block falls?  Is there a choice of distance and block mass for which the mass of the car does not make much difference to its launch velocity?

The launch velocity does depend on the car's mass, and it would affect acceleration. A heavier car would accelerate more slowly than a lighter car. The launch velocity also depends on the mass of the block and the distance at which the block falls. Heavier block mass and greater track distance would lead to a higher velocity.

If the same mass block falls through the same distance, but you change the mass of the cart, does the force that the string exerts on the cart change?  In other words, is the force of the string on object A always equal to the weight of object A?  Is it ever equal to the weight of object A?  Explain your reasoning.

It does not change since increasing the mass of the cart lowers the acceleration, so the force that the tension on the string exerts stays the same. The force of tension on the string on object A is equal to the weight of object A when the system is at rest. It is not equal when the system is moving.

Was the frictional force the same whether or not the string exerted a force on it?  Does this agree with your initial prediction?  If not, why?

This did not agree with our initial prediction. The frictional forces are not the same because the frictional force is dependent on the forces applied to the system, such as the string, and our system had different forces applied to it through the changing mass of the weights on the string. When the car first starts moving, the force comes from the string due to the block, and when the block hits the floor, the car will keep moving but slow down due to friction.