Is there an error in the answer for Impulse Momentum Linear Homework?

[freshbox]

I'm sorry I still don't understand. What acceleration got to do with netforce?

 

[Doc Al]

I'm sorry I still don't understand. What acceleration got to do with netforce?

Newton's 2nd law!

ƩF = ma

 

[freshbox]

So I_1-2= Force x Time

This is the net force but what does it represent as?

 

[Doc Al]

So I_1-2= Force x Time

This is the net force but what does it represent as?

I don't quite understand your question. It is the net force on a body that determines its change in motion.

As the system slams into the ground, the ground pushes up on it, helping to bring it to rest in the given time and distance. There are two forces involved in determining what happens to the system: gravity acting down and the much larger upward force from the ground. Combined, they give the net upward force.

 

[freshbox]

I got confused with this question part a (i). I know how to solve this question, I tried to used the same method and got the answer. But when I tried it on the previous hammer question with the working of:

M1=mv
=(9000)(8.82)
=79380

M2=mv
=0

I1-2=Force x Time
=(F)(0.1)
=0.1F

M1+I1-2=M2

79380-0.1F=0
79380=0.1F
F=793800 Ans Wrong

Because you said this is the net force and plus the rest of the explanation totally make me lost in space This 3 marks is so damn hard

 

[Doc Al]

I got confused with this question part a (i). I know how to solve this question, I tried to used the same method and got the answer. But when I tried it on the previous hammer question with the working of:

M1=mv
=(9000)(8.82)
=79380

M2=mv
=0

I1-2=Force x Time
=(F)(0.1)
=0.1F

M1+I1-2=M2

79380-0.1F=0
79380=0.1F
F=793800 Ans Wrong

Because you said this is the net force and plus the rest of the explanation totally make me lost in space This 3 marks is so damn hard

Once again: F is the net force, but they ask for the resistive force. So use the net force to solve for the resistive force. (Review post #28)

 

[freshbox]

Post #35 Question 7ai working:

M₁=mv
=1000x19.44
=19444.44

M₂=mv
=1000x16.67
=16666.67

T_1-2= F x T
=-Fx4
=-4F

M₁+I_1-2=M₂
19444.44-4F=16666.67
-4F=-2777.77
F=694.4N Answer

So this 694.4N is the net force, and there is another resistive force?

I tried to apply this style of working on the hammer question, but you told me that is the net force and ask me to find the other resistive force

I got confused here with this part and the hammer question, I hope you know what i meant...

 

[Doc Al]

Post #35 Question 7ai working:

M₁=mv
=1000x19.44
=19444.44

M₂=mv
=1000x16.67
=16666.67

T_1-2= F x T
=-Fx4
=-4F

M₁+I_1-2=M₂
19444.44-4F=16666.67
-4F=-2777.77
F=694.4N Answer

So this 694.4N is the net force, and there is another resistive force?

In this case, the net force is the 'net resistive force', so that's your answer.

I tried to apply this style of working on the hammer question, but you told me that is the net force and ask me to find the other resistive force

I got confused here with this part and the hammer question, I hope you know what i meant...

In the hammer question you had two individual forces acting: gravity and the resistive force of the ground.

In the car question they just want the net resistive force (gravity doesn't enter into it, since he's on level ground).

 

[freshbox]

Ok can, understood. Thanks for the explanation again at least I have a clearer picture now, Sorry for being too slow Tomorrow is my finals, wish me all the best!