Question

1. A baseball thrown at an angle of 65.0 ∘ above the horizontal strikes a building 18.0 m away at a point 8.00 m above the point from which it is thrown. Ignore air resistance.

A) Find the magnitude of the initial velocity of the baseball (the velocity with which the baseball is thrown).

I got 17.0 m/s

B) Find the magnitude of the velocity of the baseball just before it strikes the building.

C)Find the direction of the velocity of the baseball just before it strikes the building.

.2.Canadian geese migrate essentially along a north-south direction for well over a thousand kilometers in some cases, traveling at speeds up to about 100 km/h. One such bird is flying at 100 km/h relative to the air, but there is a 30.0 km/h wind blowing from west to east.

A)At what angle relative to the north-south direction should this bird head so that it will be traveling directly southward relative to the ground?

B)How long will it take the bird to cover a ground distance of 550 km from north to south? (Note that even on cloudy nights, many birds can navigate using the earth's magnetic field to fix the north-south direction.

Answer 1

1.

motion along horizontal

18 = v cos 65 * t

vt = 42.59...(i)

motion along vertical

8 = v sin 65 * t - 0.5 gt^2

8 = 42.59 sin 65 - 4.9* t^2

t = 2.5 s

putting in (i)

v = 17.04 m/s

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b)

using conservation of energy

0.5 m v^2 = 0.5 m v' ^2 + mgh

0.5 * 17.04^2 = 0.5* v'^2 + 9.8* 8

v' = 11.557 m/s

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c)

horizontal velocity

vx = 17.04 cos 65 = 7.2 m/s

direction

x = arccos ( vx/v' )

x = 51.456 below horizontal

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