Golf ball initial velocity and launch angle from range and flight time

[gen1pro]

Well I've been working on these last two problems and I just can't figure them out. Can someone just point me in the correct direction?

1.) A golf ball is struck with a five iron on level ground. It lands 105.0m away 3.80 s later. What is the magnitude and the direction of the initial velocity?(Neglect air resistance.)

This is what I have for this problem: V=105/3.8 = 27.63m/s
Then I used y = Vyot - (1/2)g t^2 the answer from this was 70.76 for which I then used 70.76 sin 27.63 to get an angle.

thanks in advance for the help

kwesi

 

[Fermat]

Check your working again for the velocity of 70.67.

 

[Brinx]

V=105/3.8 = 27.63m/s

Careful there, that's just the (constant) speed in the horizontal direction. If you want to use the formula $$y(t) = V_{y}(0)\cdot t - \frac{1}{2}gt^{2}$$, try to fill in the values for the moment the ball touches down again. You should end up with $$V_{y}(0)$$. Then you'll have both components of the initial velocity vector, and from there it's just a small step to complete the answer.

 

[gen1pro]

thanks for the info I was able to figure it out with your help.