Hello,

To solve this problem, we'll use the formula

v^2 - u^2 = 2as.

Here v is final velocity.

v is u/2 at distance s=3cm.

We have to find the value of a.

Substituting the values, we get:

a= -1 * (u^2 / 12). ----- Let this be equation 1.

In case 2, using the same formula,

now, initial velocity u is u/2. Final velocity v is 0.

a is substituted from eq. 1.

Hence we get, 0 - (u/2)^2 = 2 * s * (-u^2/12)

Therefore, s = 3cm. This is the distance the target travels before coming to rest.

Hope this helps.

Thanks.