Which of the following is the law of conservation of momentum?
(Points : 3)
The impulse acting on any object is the change in momentum that it causes.

When two objects interact within a closed system, neither one changes its momentum.

In the absence of any external force, the total momentum of a system stays the same.

The acceleration of any object is equal to the net force acting on it divided by its mass.

Question

Which of the following is the law of conservation of momentum?
 (Points : 3)  
       The impulse acting on any object is the change in momentum that it causes.

        When two objects interact within a closed system, neither one changes its momentum.

        In the absence of any external force, the total momentum of a system stays the same.

        The acceleration of any object is equal to the net force acting on it divided by its mass.

caozeyuan · Answer

conservation means "stay the same"

caozeyuan · Answer

so which choice says momentum stays the same?

anonymous · Answer

d?

anonymous · Answer

A 1,600 kg car traveling north at 10.0 m/s crashes into a 1,400 kg car traveling east at 15 m/s at an unexpectedly icy intersection. The cars lock together as they skid on the ice. What is their speed after the crash?
 (Points : 3)  
       8.8 m/s

        12 m/s

        18 m/s

        26 m/s

caozeyuan · Answer

No, should be C

caozeyuan · Answer

D is N2 right?

anonymous · Answer

whats that for question 1 right?

caozeyuan · Answer

Yes Q1 is C

anonymous · Answer

q2 now?

caozeyuan · Answer

$$m _{1}v_{1}+m _{2}v _{2}=(m _{1}+m _{2})V$$

caozeyuan · Answer

This is your eqn for Q2. It comes  conserv of P

anonymous · Answer

help plug it ?

caozeyuan · Answer

since the only variable is V, you can solve for it

caozeyuan · Answer

m1 is the mass of first object, m2 is mass of second object

caozeyuan · Answer

v1 is velocity of first, v2 is velocity of second

anonymous · Answer

yes

caozeyuan · Answer

understand now?

anonymous · Answer

a little plug it in fully and ill do the rest please ?

caozeyuan · Answer

1600*10+1400*15=3000*V

caozeyuan · Answer

now you can do it

anonymous · Answer

okay then i divide 3000 by the velocity

anonymous · Answer

what do i do now?

anonymous · Answer

so b?

caozeyuan · Answer

yes

anonymous · Answer

good okay new one?

anonymous · Answer

In which case is a collision between two objects completely inelastic?
 (Points : 3)  
       The two objects bounce off each other at the same speed as before.

        The two objects stick together.

        The two objects leave at +30° and 30° from the original direction.

        The sum of the velocities of the two objects is the same before and after

caozeyuan · Answer

B, this is the most obvious case of IEC

anonymous · Answer

awee okay now?

anonymous · Answer

Which of these barbells has the smallest rotational inertia when rotated as shown? The arrow shows the axis and the way that torque is applied. Assume the weights positioned on the barbells all have the same mass.


 (Points : 3)  
       barbell A

        barbell B

        barbell C

        barbell D

anonymous · Answer

attachment

caozeyuan · Answer

B, cause it has the shortest distance

caozeyuan · Answer

help me with one Q pls？

anonymous · Answer

If the angular momentum of an object increases, which of these could be true?
 (Points : 3)  
       The moment of inertia increased.

        The angular velocity of the object decreased.

        The mass of the object decreased.

        The object's moment of inertia decreased.
 & okay!

caozeyuan · Answer

I would say both C and D

anonymous · Answer

but which one i can only pick 1

caozeyuan · Answer

No, my bad!

caozeyuan · Answer

should be A cause he Q says INCREASE

michele_laino · Answer

I think the right answer is the third, namely:
" In the absence of any external force, the total momentum of a system stays the same."