maths urgent please please

Original post by khalizo123

Peter aims straight across the river, and is carried downstream by the current.
i How long does he take to reach the other side?
il Work out his actual speed of travel. b Mary swims to the closest point on the opposite bank.
i In which direction does she aim? ii Work out her actual speed of travel.
ili How long does it take her to reach the other side?

There must be a diagram and/or some additional information that goes with this question, like the width of the river, the speed of the current and the speed with which the two people can swim through the water.

Reply 2

OP

Original post by old_engineer

There must be a diagram and/or some additional information that goes with this question, like the width of the river, the speed of the current and the speed with which the two people can swim through the water.

here it is

Reply 3

OP

Original post by khalizo123

here it is

A river flows at 0.3 ms. Peter and Mary, who can each swim at 0.5 ms' in still water, wish to cross the river. The river is 20 metres wide.Peter aims straight across the river, and is carried downstream by the current.
i How long does he take to reach the other side?
il Work out his actual speed of travel. b Mary swims to the closest point on the opposite bank.
i In which direction does she aim? ii Work out her actual speed of travel.
ili How long does it take her to reach the other side?

Reply 4

Original post by khalizo123

A river flows at 0.3 ms. Peter and Mary, who can each swim at 0.5 ms' in still water, wish to cross the river. The river is 20 metres wide.Peter aims straight across the river, and is carried downstream by the current.
i How long does he take to reach the other side?
il Work out his actual speed of travel. b Mary swims to the closest point on the opposite bank.
i In which direction does she aim? ii Work out her actual speed of travel.
ili How long does it take her to reach the other side?

OK, so what have you tried, and where are you stuck?

Reply 5

OP

idk how to do it

Original post by old_engineer

OK, so what have you tried, and where are you stuck?

Reply 6

Original post by khalizo123

idk how to do it

For part (i), Peter is swimming in a direction straight across the river. He is swimming perpendicular to the current, so the current does not affect his progress in the direction across the river. He is swimming at 0.5m/s and has to cover 20m. So how long does it take?

Reply 7

OP

40s

Original post by old_engineer

For part (i), Peter is swimming in a direction straight across the river. He is swimming perpendicular to the current, so the current does not affect his progress in the direction across the river. He is swimming at 0.5m/s and has to cover 20m. So how long does it take?

Reply 8

Original post by khalizo123

40s

Yes. Now for part (ii) he is moving at 0.5m/s across the river and 0.3m/s down the river, with the current. That's two components of velocity at right angles to one another. So what is his speed across the ground?

Reply 9

OP

idk could u give me a formula

Reply 10