Hanging Mass with Car Lab

   

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

The measured velocity seemed to be slightly smaller than our predictions. Our predictions were a little higher and the difference between both weren't far off but there was a difference. I believe the differences were due to a couple reasons. One being in the friction in the track that the car rode on and the friction between the string and the pulley. Although it is small, there is still friction that was unaccounted for. The other problem could have been due to the release of the car. There could have been small accidents/changes on the last second before the car was let go, maybe pushing or pulling it on accident.

Does the launch velocity of the car depend on the 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? 

I believe the velocity of the car depends on the mass of the car, mass of the block and distance the block falls. I believe the mass of the car plays a role because a heavier car will need more force to make it go a faster velocity. If the car is light, it is easier to speed it up. The mass of the block also plays a factor because if a big heavy block is dropped, that momentum will bring the string down fast and stronger, therefore pulling the car with more velocity. The distance the block falls also plays a role because the more the mass falls, the more it pulls with momentum. If the block hits the floor immediately, the car is just rolling with no acceleration. I believe if the block weighs a lot and the distance is great, the heavier car will still have a great 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 the object A? Explain your reasoning?

No, the force the string exerts on the card does not not. This is because the tension the string holds is equal to the force exerted on the car, meaning the tension changes depending on the point the car is in. The tension is equal the weight of object A when the mass is just dangling the falling straight down. In a FBD, the force would just be the tension up and the force of gravity pointing down. The tension does change depending on the weight of the object though. The lighter the block, the lower the tension.

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

No, the frictional force is not the same when the string exerted a force on the system. This is because when the string is connected and pulling it while the block is falling, the friction is pushing against the car but the mass falling is overpowering this friction, causing it to continue to keep moving. If the car stops, this is because there is no more energy coming from the block and the car is just freely moving, but the friction is not being overpowered so it will stop the car. This is similar to the initial position.