# Vector projectile

1. May 19, 2005

### benzun_1999

help me pls
if the initial velocity of a projectile at the highest point of trajectory is equal to half of the initial velocity of projection, calculate the angle of projection.

can anyone help me

2. May 19, 2005

### arildno

First of all, say "speed" rather than velocity here!

Furthermore:
1) What is the vertical velocity component at the highest point of the trajectory?
2) Does the horizontal velocity component change during projectile motion?
(I have assumed that air resistance is negligible)
3) How is the initial horizontal velocity component related to the initial speed and angle of projection?

Try to formulate answers to these questions.

3. May 26, 2005

### benzun_1999

it is not speed.
sorry for the late reply as i had exams. This question is from my physics question paper. the question is as i have written. no more info was give. only g acts here. note that at the higest point of a projectile the vertical v=0 but the horizontal velocity remain the same unaltered.

Last edited: May 26, 2005
4. May 26, 2005

### whozum

$$v_0^2 = v_x^2 + v_y^2$$

When [itex] v_y^2 = 0, v_x = \frac{1}{2} v_0 [/tex]

Draw yourself a triangle.

5. May 26, 2005

### benzun_1999

$$v_m_a_x_h = 0$$
[itex]v_i_n_t_i = 1/2 v_m_a_x [/tex]
v max= 0 therefore 1/2 of 0 = 0 whis not the correct answer.

Last edited: May 26, 2005
6. May 26, 2005

### whozum

at h = hmax, vy = 0, vx however is not zero.

7. May 26, 2005

### benzun_1999

therefore u are telling that
$$v_m_a_x = 1/2 v_x$$
which implies that
[itex] v_m_a_x = 1/2 u cos x [/tex]
i think u are right.
i made a mistakwe here only.
i knew all other questions but this one confused me a lot. anyway thank u

8. May 26, 2005

### whozum

Do you understand WHY all this happens though?

9. May 26, 2005

### benzun_1999

no
it just didnt strike me.
moreover i was not there when sir explained this sum before the exam

Last edited: May 26, 2005
10. May 26, 2005

### whozum

So you do understand, or you dont?
Would you like me to explain why?

11. May 26, 2005

### benzun_1999

i understand,
but i didnt understand the 2nd part of ur question

12. May 26, 2005