Question

A toy plane P starts flying from point A along a straight horizontal
line 20 m above ground level starting with zero initial velocity
and acceleration 2 m/s2 as shown. At the same instant, a man
P throws a ball vertically upwards with initial velocity 'u'. Ball
touches (coming to rest) the base of the plane at point B of
plane's journey when it is vertically above the man. 's' is the
distance of point B from point A. Just after the contact of ball
with the plane, acceleration of plane increases to 4 m/s. Find:
Initial velocity 'u' of ball.
Distance 's'.
Distance between man and plane when the man
catches the ball back. (g = 10 m/s)​

Answer 1

Answer:

◆ Answer -

(d) |AB| = 8.5 m

● Explaination -

Let i, j & k be unit vectors along X-axis, Y-axis & Z-axis.

A = i + 2j - 3k

B = 3i + 4j + 5k

Displacement of the man is calculated by -

AB = B - A

AB = (3i + 4j + 5k) - ( i + 2j - 3k)

AB = 2i + 2j + 8k

Magnitude of displacement is calculated by -

|AB| = √(2² + 2² + 8²)

|AB| = √(4 + 4 + 64)

|AB| = √(72)

|AB| = 2√18

|AB| = 8.48 m

From the options, 8.5 m is the most appropriate.

Answer 2

Answer:

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