-- We're pretty sure that this question is based on an assumption of EARTH, so we know that we're dealing with a sphere of roughly 3.950 miles radius.
-- The distance on the sphere between 30° west and 60° east is 90° of longitude. That's 1/4 of the total circumference of the circle.
-- BUT ..... Way up here at 60° N latitude, the circle is not as big as the equator. It's radius/diameter/circumference is only cos(60°) = 0.5 of the Earth's total.
-- So the length of our quarter-circle arc is about
(1/4) x (2 · π · 3,950 miles) x (0.5) =
(1/4) x (3,950 π miles) =
988 π miles = 3,104 miles
Answer:
2.4 m/s
Explanation:
Given:
Velocity of the object moving north = 2.1 m/s
Velocity of the river moving eastward = 1.2 m/s
The resultant velocity is the vector sum of the velocities of object and river.
Since the directions of velocity of object and river are perpendicular to each other, the magnitude of the resultant velocity is obtained using Pythagoras Theorem.
The velocities are the legs of the right angled triangle and the resultant velocity is the hypotenuse.
The magnitude of the resultant velocity (R) is given as:

Therefore, the resultant velocity has a magnitude of 2.4 m/s.
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Kinetic energy = momentum^2 / 2 x mass
Mass = (momentum^2/ Kinetic energy) / 2
Mass = (25^2 / 275) / 2
Mass = 1.136 kg.
momentum = mass x velocity
velocity = mass / momentum
velocity = 1.136 / 25
velocity = 0.04544 m/s