Question
IMU
Question 4
The thrust
of a propeller varies jointly as the square of the number
of revolutions per second
and the fourth power of its diameter
. What is the effect on
if
is doubled and
is halved?
( 3 marks)
Question 4
The thrust
and the fourth power of its diameter
( 3 marks)
Ask by John Love. in Australia
Jan 19,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
When the number of revolutions per second is doubled and the diameter is halved, the thrust becomes one fourth as large.
Solution

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Mind Expander
To solve this problem, we start with the relationship given by the formula for thrust
:
where
is a constant of proportionality. Now, if we double the number of revolutions per second
(so it becomes
) and halve the diameter
(so it becomes
), we can substitute these values into the thrust equation:
Calculating this gives:
Simplifying this, we have:
Thus, we find:
This means that if
is doubled and
is halved, the thrust
becomes one-quarter of the original thrust
. So the effect on thrust is a reduction to just 25% of its original value.