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# m3 help further kinematics watch

1. not sure how to work this out. any help please?
2. (Original post by Cheesegrater4)

not sure how to work this out. any help please?
Have you done differential equations in C4?
3. (Original post by MK_)
Have you done differential equations in C4?
yes
4. (Original post by Cheesegrater4)
yes
Oops, I misread at first, I thought the problem was with solving the de rather than setting it up. Do you understand where the left hand side comes from? If not, think about acceleration as a differential and then use the chain rule to express it in terms of v and x. Then the right hand side comes from Newton's 2nd Law and realising that 'increases uniformly with the distance moved' means that the resistive force is proportional to the distance travelled.
5. i get that acceleration = v dv/dx but i don't get what you mean about using newtons second law?
6. (Original post by Cheesegrater4)
i get that acceleration = v dv/dx but i don't get what you mean about using newtons second law?
The net force on the object is equal to mass*acceleration, and you have the acceleration for two values of x.
7. (Original post by Cheesegrater4)
i get that acceleration = v dv/dx but i don't get what you mean about using newtons second law?
you don't need Newtons second law. You are told what the acceleration is so just put (v)dv/dx = to that expression.

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