Question

Help explain this problem!!!! i will give medal :p

Answer 1

An arrow is fired with a horizontal speed of 89 m/s directly at a target 60 m away. When it is fired, the arrow is 1 m above the ground. How far short of the target is it when it strikes the ground? Ans: 20 m short

i know the answer but i don't understand how to get there. help please!

Answer 2

http://www.physicsclassroom.com/class/vectors/u3l2e.cfm
This will help

Answer 3

So, in this problem, the important distinction to make is that horizontal and vertical motion do not rely on one another. They are completely independent. This question gives a lot of information about the horizontal motion, but the only information we really need to notice is the height, which is 1 m above the ground.

The projectile is fired completely horizontal, so all 89 m/s is in the x direction and does not play a role in the object falling. The only factor in the object's fall is gravity, at -9.8 m/s^2.

To solve this problem, simply calculate how long it will take the object to hit the ground. The time taken to hit the ground is given just by the definition of acceleration:\[d=\frac{ 1 }{ 2 }at^{2} \rightarrow t=\sqrt{\frac{ 2d }{ a }}\]This gives us:\[t=\sqrt{\frac{ 2(1) }{ 9.8 }}=0.45 s\]
Now, we simply have to use this time with the velocity given to find the distance traveled by the projectile. The time is how long it will remain in the air, so let's see how far it gets.
Displacement is defined as velocity multiplied by time, so let's use that:\[d=vt=(89)(0.45)=40m\]
As you can see from the answer of 40m, this is 20m less than the 60m to the target.

Answer 4

so 60m is not needed in the problem until the end, ok thanks, the 60m horizontal distance was confusing me, :p thanks

Answer 5

Yep, 60m just acts as the comparison!