# OCR M4- misinterpreted question?Watch

#1
Sorry to ask so many Mechanics questions - self-teaching M3/4 on a gap year for STEP is throwing up more obstacles than I imagined!

The question giving me trouble this time is: A bag of rubbish is thrown off a ferry travelling at 12ms^-1, with a horizontal velocity of 6m/s at 50 degrees to the direction of motion of the ship. If it lands in the sea 3 seconds later, what horizontal distance does it appear to travel before hitting the sea as observed by a person standing on the harbour wall?

I interpret this to mean that the ship must be travelling at 50 degrees to the horizontal. So we just want to add the horizontal components of both velocities and then multiply by 3. e.g 3 *(6 + 12cos(50)). However this is NOT the answer of 49.5 given by the textbook. Am I misinterpreting the situation, or is there an error in the solutions ... ?
0
2 years ago
#2
(Original post by MaffsIsFun)
Sorry to ask so many Mechanics questions - self-teaching M3/4 on a gap year for STEP is throwing up more obstacles than I imagined!

The question giving me trouble this time is: A bag of rubbish is thrown off a ferry travelling at 12ms^-1, with a horizontal velocity of 6m/s at 50 degrees to the direction of motion of the ship. If it lands in the sea 3 seconds later, what horizontal distance does it appear to travel before hitting the sea as observed by a person standing on the harbour wall?

I interpret this to mean that the ship must be travelling at 50 degrees to the horizontal. So we just want to add the horizontal components of both velocities and then multiply by 3. e.g 3 *(6 + 12cos(50)). However this is NOT the answer of 49.5 given by the textbook. Am I misinterpreting the situation, or is there an error in the solutions ... ?
Solution is correct.

Your interpretation of the ship travelling at "50 degrees to the horizontal" is the problem. In that postion, it would be just about to capsize, I'd think.

Everything of relevance is taking place on the horizontal plane. If you imagine the set up of the ship heading North say, and the bag is thrown on a bearing of 050 degrees (the situation doesn't give you bearings, but the example will hopefully show you what the general set up is). And they're looking for the horizontal distance travelled by the bag.
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