forgetyourself

Hi Imat Thank you so much for the tips . That's a great help to me. ill keep all your advice in minD when sit down to tackle this one again.

Thanks imatfaal. But im still stuck. How would i know the rate of deceleration of the knife penetrating the ground. Is it a constant? Thanks!

Hi all, i am forgetyourself and i love environmental studies, and struggle with physics. I will be happy to help anyone with environmental stuff and desperately need help with physics. I think this forum is excellent.

Please help if anyone can a knife hits the ground at a speed of 40 m s-1. It penetrates the ground to a depth of 30 cm. Acceleration due to gravity is 9.81 m s-2. How can i find the deceleration of the knife. I know the following equation might help; speed = distance / time acceleration = change in speed / time I also know that the knifes speed initial speed when it hits the ground is 40 m s-1 and its final speed is 0 ms-1. So its change in speed is 40ms-1. But I dont know how to find the time, and i dont know if i am using the correct equations for this question. Ive been reading my physics books for hours now but cannot figure it out. I would really appreciate any help. Can (Ek = 1/2 mv squared) help me?