Solve Physics 12 Help Problems: Change in Momentum & Diagrams

[God64bit]

Problem 1
A 12.0 kg shopping cart rolls due south at 1.50 m/s . After striking the bumper of a car, it travels at 0.80 m/s, 30° E of S. What is the magnitude of the change in momentum sustained by the shopping cart?

a drew a free body diagram used the formula
Pyo + Py1 = P'yo + P'y1 and Pxo + Px1 = P'xo + P'x1
Py1 is some mithical object or the car which i am assumeing isn't moveing I am takeing the y direction of its momentom gained + the X direction of its momentom gained adding them together yields
Sqare root of ((12(1.5)-12sin(60)(.8))^2 + (12sin(30)0.8)^2 = 11.8
now here's the problem 11.8 is not an answer what did i mess up? it doesn't seem like a calculator error wheres my thinking wrong?

Problem 2
Diagram = http://quizmebc.ca/images/exams/4010113.gif

x= the object labeled x
C for center of the beam
o for the object on the right
Assume clockwise negative
Sigma t = FxLx + FcLc - FoLo = 0
Rearranged
Lx=FcLc - FoLo / -Fx = 0
(.122)(9.8)(.2) - (.5)(9.8)(.25) / - (.2)(9.8) = Lx
Lx= 1.753 ... hmm considering the length of the entire bar is .9m i think something is wrong...

I'll probally end up have 6 or 7 questions today... i am allowed to ask so many ... dumb questions? (been going through and every 10-15 questions things just don't work right for some very odd reason.)
(big test and no one around for miles that knows theirs a diffrence between mass and wieght...)

 

[dx]

after hitting the bumper, the south component of the momentum is 12x0.8 cos 30 (you can see this from the diagram you drew). Find the difference in the south component before and after. Since the initial east component is zero, the change in east component is simply 12x0.8 sin30.

 

[kyle8921]

I would like to provide some guidance and suggestions for solving these physics problems.

For Problem 1, it seems like you have correctly used the formula for change in momentum, but there may have been some errors in your calculations. I would suggest double checking your math and using the correct values for the angles (60 degrees and 30 degrees). Also, make sure to include the units in your final answer, which should be in kg*m/s.

For Problem 2, it is important to clearly define the variables and use the correct equations. I am not sure what values you used for Fx, Fc, and Fo, but it is important to use the correct forces and their corresponding distances from the pivot point. Also, remember to include the units in your final answer, which should be in N*m.

In general, when solving physics problems, it is important to clearly define the variables, use the correct equations, and pay attention to units. It may also be helpful to draw a diagram and label all the forces and distances involved. If you are unsure about any concepts or calculations, it is always helpful to seek clarification from a teacher or tutor. It is also completely normal to have questions and make mistakes when learning new material, so don't be afraid to ask for help. Good luck with your studies!