Does the Golf Ball Land Before, In, or After the Lake?

AI Thread Summary
A golfer hits a ball at 40 m/s at a 45-degree angle towards a lake 100 m away. Initial calculations suggested the ball lands 79 m from the start, indicating it would land before the lake. However, the time calculated was only for half the flight, leading to an incorrect distance. Correcting this by using the total flight time reveals the ball actually lands 160 m away, which is beyond the lake. The discussion emphasizes the importance of understanding the context of calculations in physics problems.
rasen58
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Homework Statement


Golfer hits a golf ball so that it goes with initial velocity of 40 m/s at angle of 45 degrees. 100 m away is a lake that is 50 m wide. The ball will not bounce or roll when it lands. Where does the ball land?
Before, in, or after the lake.

Homework Equations


Vertical: a = (v-v0)/t
Horizontal: Δx = v0t+1/2at2

The Attempt at a Solution

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I found the time as 2.8 s using the first equation by setting v = 0 (midway in flight), and v0 = 40sin45
Then I substituted the time into the second equation along with 0 for the acceleration since there is no horizontal acceleration and v0 = 40cos45. And got 79 m, so the ball lands before the lake.
But apparently the answer is that it lands after the lake.
What did I do wrong?
 
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rasen58 said:
2.8 s
This is the time for what?
 
The time to travel halfway.
Oh... I should've used twice that to get the total time. I get 160 m now.
Thanks, my mistake.
 
Always try to keep in mind what information you get from a calculation, and what information you've been asked to find.
 
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