Question

9.In the above question, the change in speed is:
(a) u cos 0 (b) u (c) u sine (d) (u cos 6-u)​

Answer 1

Answer:

d) ucos6-u

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Answer 2

(d) u cosθ-u

The initial velocity is u⃗ =(ucosθ,usinθ),u→=(ucos⁡θ,usin⁡θ), so that the initial speed is

|u⃗ |=(ucosθ)2+(usinθ)2−−−−−−−−−−−−−−−−√=|u|.|u→|=(ucos⁡θ)2+(usin⁡θ)2=|u|.

At the highest point, u⃗ u→ becomes

(ucosθ,0),(ucos⁡θ,0),

and the corresponding speed here is

(ucosθ)2+02−−−−−−−−−−−√=|u||cosθ|.(ucos⁡θ)2+02=|u||cos⁡θ|.

Thus, the change in speed is

|u||cosθ|−|u|,|u||cos⁡θ|−|u|,

or since