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# Mechanics Projectile Question watch

1. A golf ball is struck by a golf club from a point on flat, horizontal ground. It leaves the ground at an angle of 40 to the horizontal. 2 seconds after being struck, the ball is travelling upwards at an angle of 10 to the horizontal. Find the speed of projection and the height of the ball above the ground 2 seconds after being struck by the golf club

The answers are 38.6ms-1 and 30.0m.

Thanks
2. where did you get stuck ?
3. (Original post by the bear)
where did you get stuck ?
The part about the 2 seconds and thus the change in angle
4. the horizontal speed is constant at Vcos40°

the vertical speed at the start is Vsin40°

the vertical speed after 2 seconds is Vsin40° -9.8*2

the ratio of the two speeds is the tan of the angle at that point
5. (Original post by the bear)
the horizontal speed is constant at Vcos40°

the vertical speed at the start is Vsin40°

the vertical speed after 2 seconds is Vsin40° -9.8*2

the ratio of the two speeds is the tan of the angle at that point
"the ratio of the two speeds is the tan of the angle at that point" what does this mean?
6. (Original post by MastaV)
"the ratio of the two speeds is the tan of the angle at that point" what does this mean?
if you divide the vertical component by the horizontal component you get the tan of the angle at which the object is moving.
7. (Original post by the bear)
if you divide the vertical component by the horizontal component you get the tan of the angle at which the object is moving.
This is what I have derived:

vsin40/vcos40=tan40
and
2xvsin40/vcos40=tan10
8. (Original post by MastaV)
This is what I have derived:

vsin40/vcos40=tan40
and
2xvsin40/vcos40=tan10
the first one is right.

the second one should say

{Vsin40° -9.8*2 }/Vcos40° = tan10°
9. (Original post by the bear)
the first one is right.

the second one should say

{Vsin40° -9.8*2 }/Vcos40° = tan10°
Makes me wonder why you're not on the list for Most Helpful Member in Study Help
10. (Original post by Mystelle)
Makes me wonder why you're not on the list for Most Helpful Member in Study Help
i know what it is like to struggle with math.

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