Displacement and velocity

[cosmic]

Hi guys,

Would appreciate any guidance in regard to this question.

An object moves in a straight line and its displacement s at time t is s = 6t⁶ - 4t⁴ + 2. What is the velocity of the object at time t = 7.

I calculated the velocity v = 599564. Would be greatful if someone could check whether that is indeed the correct answer or point me in the right direction if it's incorrect.

Thanks in advance.

 

[Quaid]

Your answer matches mine, but what are the units? :cool:

 

[cosmic]

Your answer matches mine, but what are the units? :cool:

Thanks Quaid.

I wasn't given any units so I presume they're not required. The question asks to give the answer to the nearest whole number which even though sounds really simple has me confused for some strange reason lol. Should it be 599560, 599600 or 600000? I know it's a stupid question but going through it over and over in my mind has caused some doubt lol.

 

[Quaid]

I wasn't given any units so I presume they're not required.

Seems odd to report velocity without units, but okay.

The question asks to give the answer to the nearest whole number

The set of Whole numbers is simply the set of non-negative Integers, so the answer is already a Whole number.

 

[cosmic]

Seems odd to report velocity without units, but okay.




The set of Whole numbers is simply the set of non-negative Integers, so the answer is already a Whole number.

I've made a mistake the initial displacement at time t should have been -6t⁶ - 4t⁴ + 2.

Therefore I got -610540 as the answer which is negative. So what is that to the nearest whole number? Is it 1? lol Just seems so absurd to round such a high negative number to 1 as the answer. I originally thought the answer must be in decimals if it's asking for it to be given to the nearest whole number. Any thoughts?

 

[HallsofIvy]

If that is the situation then the problem should have said "to the nearest integer".

 

[cosmic]

If that is the situation then the problem should have said "to the nearest integer".

Hi and thank you for your reply.

So what do you think the question means by asking to 'give your answer to the nearest whole number'?

 

[Quaid]

So what is [-610540] to the nearest whole number? Is it 1?

No. Zero is the first non-negative Integer.

 

[Quaid]

So what do you think the question means by asking to 'give your answer to the nearest whole number'?

The meaning is ambiguous. Maybe the author used sloppy wording. After all, the answer has no fractional part, so why mention rounding.

You correctly differentiated the position function, and you correctly evaluated the derivative at the specified input.

Rounding is probably not needed, but you can always turn in two answers, with an explanation, if you feel the need.

 

[cosmic]

No. Zero is the first non-negative Integer.

But zero isn't positive or negative so wouldn't the first whole number be 1 (if whole numbers are assumed to be positive)?

The meaning is ambiguous. Maybe the author used sloppy wording. After all, the answer has no fractional part, so why mention rounding.

You correctly differentiated the position function, and you correctly evaluated the derivative at the specified input.

Rounding is probably not needed, but you can always turn in two answers, with an explanation, if you feel the need.

The problem is that's it's a computer quiz and is automatically marked by the computer so you only get the marks for getting the correct answer so I can't put two answers. :sad:

 

[HallsofIvy]

But zero isn't positive or negative so wouldn't the first whole number be 1 (if whole numbers are assumed to be positive)?

But they aren't. The "natural numbers" or "counting numbers" are the positive integers. The "whole numbers" are the non-negative integers.

The problem is that's it's a computer quiz and is automatically marked by the computer so you only get the marks for getting the correct answer so I can't put two answers. :sad:

If the problem was exactly as you stated, it's a really bad problem! I suggest you just enter the integer solution you got.

 

[cosmic]

But they aren't. The "natural numbers" or "counting numbers" are the positive integers. The "whole numbers" are the non-negative integers.




If the problem was exactly as you stated, it's a really bad problem! I suggest you just enter the integer solution you got.

Yeah I just realised that whole numbers are the non-negative integers so zero is classed as a whole number even though it's not positive.

I think I'll take your advice since it would be kind of retarded if they expect you to round such a huge negative integer to zero. Whoever came up with the question deserves shooting.

Once again thanks for you help.

 

[Quaid]

I just realised that whole numbers are the non-negative integers

Sorry to hear this; we posted that information two days ago.

If you're taking an exam which has no recourse for institutional errors, sorry to hear that, too.