Simple projectile motion - problem with units

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SUMMARY

The forum discussion centers on a projectile motion problem involving a ball with a mass of 0.4 kg, launched at a velocity of 17 m/s at an angle of 42° above the horizontal. The key issue is the incorrect unit specifications in the homework, where time is requested in Newtons (N) and height in seconds (s), leading to confusion among participants. The consensus is that these units are likely typos, and the correct answers should be in seconds for time and meters for height. Participants emphasize the need for clarity in unit specifications to avoid misunderstandings.

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Jack_Straw
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Homework Statement



(a) A ball of mass 0.4 kg, initially at rest, is kicked directly toward a fence from a point 20 m away, as shown below.
The velocity of the ball as it leaves the kicker’s foot is 17 m/s at angle of 42◦ above the horizontal. The top of the fence is 5 m high. The ball hits nothing while in flight and air resistance is negligible.
The acceleration due to gravity is 9.8 m/s2.
Determine the time it takes for the ball to reach the plane of the fence.
Answer in units of N.

(b) How far above the top of fence will the ball pass? Consider the diameter of the ball to be
negligible. Answer in units of s.

Homework Equations



irrelevant for question

The Attempt at a Solution



This problem seems quite easy. The problem is that its asking for the answer in units of N. How can I express time in Newtons?

The same problem occurs in question b. I know how to calculate the answer, but how can I express height in seconds?

I have tried inputting the answers as if they are supposed to be in seconds for number one and feet for number two (assuming the "answer in units of N" and "answer in units of s" are typos) but I'm greeted with the message, "sorry that answer is incorrect, try again."

What am I missing here?
 
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Jack_Straw said:

The Attempt at a Solution



This problem seems quite easy. The problem is that its asking for the answer in units of N. How can I express time in Newtons?

The same problem occurs in question b. I know how to calculate the answer, but how can I express height in seconds?

I have tried inputting the answers as if they are supposed to be in seconds for number one and feet for number two (assuming the "answer in units of N" and "answer in units of s" are typos) but I'm greeted with the message, "sorry that answer is incorrect, try again."

What am I missing here?

It really does appear that those units are typos, in both (a) and (b). (And hopefully your answer for (b) was in meters, not feet?)

If you're willing to post your work, we (real humans) could at least check your answers.
 

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