Exam 4: Motion in Two and Three Dimensions

A girl wishes to swim across a river to a point directly opposite as shown.She can swim at 2 m/s in still water and the river is flowing at 1 m/s.At what angle $\theta$ with respect to the line joining the starting and finishing points should she swim?

A stone is tied to a 0.50-m string and whirled at a constant speed of 4.0 m/s in a vertical circle.Its acceleration at the top of the circle is:

The velocity of a projectile equals its initial velocity added to:

A jet plane in straight horizontal flight passes over your head.When it is directly above you, the sound seems to come from a point behind the plane in a direction 30 $\degree$ from the vertical.The speed of the plane is:

A motor boat can travel at 10 km/h in still water.A river flows at 5 km/h west.A boater wishes to cross from the south bank to a point directly opposite on the north bank.At what angle must the boat be headed?

Identical guns fire identical bullets horizontally at the same speed from the same height above level planes, one on the Earth and one on the Moon.Which of the following three statements is/are true? I.The horizontal distance traveled by the bullet is greater for the Moon. II.The flight time is less for the bullet on the Earth. III.The velocities of the bullets at impact are the same.

An object is moving on a circular path of radius $\pi$ meters at a constant speed of 4.0 m/s.The time required for one revolution is:

A ball is thrown horizontally from the top of a 20-m high hill.It strikes the ground at an angle of 45 $\degree$ .With what speed was it thrown? Use g = 10 m/s².

Which of the following is a vector quantity?

Which of the curves on the graph below best represents the vertical component v_y versus t for a projectile fired at an angle of 45 $\degree$ above the horizontal?

A plane traveling north at 200 m/s turns and then travels south at 200 m/s.The change in its velocity is:

A particle moves at constant speed in a circular path.The instantaneous velocity and instantaneous acceleration vectors are:

A boy wishes to cross a river in the shortest possible time, without necessarily landing directly across from his starting point.He can row at 2 m/s in still water and the river is flowing at 1 m/s.At what angle $\theta$ should he point the bow (front)of his boat?