# help pls (1 Viewer)

#### kkk579

##### hello
ignoring part a, for part b do i have to put a negative in front of s? cos i keep getting a negatuve value when it shoukd be positive. the answer to a is 0.77 so u dont gotta work it out and b is 0.31

#### kkk579

##### hello
I did it using conversation of energy + momentum conversation. Initially the GPE = (9.8)(0.5)(1.5)=7.35 J. All of this gets converted to KE thus 1/2mv^2=7.35 --> solve for v and you get approx 5.422m/s. Then conservation of momentum so m1v1= m2v2 thus (0.5)(5.422)=3.5v2 --> solving for v2 u get 0.77m/s

Ill see if I can do part b tmr since its late but hopefully this helps
Yeah part a is fine ik how to do it i just said ignore it since u only need the answer for part a to do part b but thank you anyways!

#### kkk579

##### hello
Yea my bad aha I didnt really read ur thing - for b I think its cause on the LHS ur velocity should be 0.77^2 - 0 (initial - final))
Isnt change in ke =1/2m(v squared - u squared)?

##### Member
yea thats mb im tripping rn haha - I think the difference in velocity is squared not the difference of them squared

#### kkk579

##### hello
yea thats mb im tripping rn haha - I think the difference in velocity is squared not the difference of them squared
? I wrote 0 squared minus 0.77 squared LMAO

#### liamkk112

##### Well-Known Member
ignoring part a, for part b do i have to put a negative in front of s? cos i keep getting a negatuve value when it shoukd be positive. the answer to a is 0.77 so u dont gotta work it out and b is 0.31
View attachment 43065
distance is always positive so yeah it should be. it’s just a matter of taking absolute value at the end, or u can define the direction of the friction force to be negative so the answer works out, either one works

#### kkk579

##### hello
distance is always positive so yeah it should be. it’s just a matter of taking absolute value at the end, or u can define the direction of the friction force to be negative so the answer works out, either one works
Ohhhh yeahh i forgot that i should make friction negative thank you