Questions 11 to 13 fer to the following information: 30 100 m 8.77 m A ball is p

Question

Questions 11 to 13 fer to the following information: 30 100 m 8.77 m A ball is projected from a 10 m high vertical building at an angle of 30° above the horizontal and hits the ground a horizontal distance of 8.77 m from the base of the building after 1.75 seconds. Assume that air resistance is negligible. QUESTION 11 Which one of the following statements about the horizontal motion of the ball is true? (a) The horizontal velocity of the ball will be 5 ms (b) The horizontal acceleration of the ball will be zero. (c) The horizontal velocity at any time during will equal the initial horizontal velocity. (d) All of these are true. QUESTION 12 The initial speed of the ball will be closest to (a) 4 m s (b) 5 m s (c) 6 m s (d) 10 m s QUESTION 13 Just at the instant before the ball strikes the ground, the magnitude of the vertical component of the velocity will be closest to (a) 200 m s (b) 14.3 m s (c) 20.1 m s (d) 14.6 m s

Explanation / Answer

11) a) S= ut

intial velocity, u= s/t

= 8.77/1.75

= 5.011

aprrox 5.

b) since no force is acting on the ball in the horizontal direction, therefore horizontal acceleration will be ZERO.

c) Since acceleration in the horizontal direction is zero therefore initial horizontal velocity is equal to final horizontal velocity.

Since all the above options are true

correct answer will be D) all the above.

12) Horizontal speed= 5 m/s

let the initial velocity = v m/s

Now, v cos30= 5 m/s

v= 5/ cos30

v= 5*2/ root3 (cos30 = (root3)/2)

v= 5.774

v= 6 m/s (approx)

13) Initial vertical velocity vi= v sin30= 5/(root3)

final vertical velocity= vf

vf^2=vi^2+2gh

vf= root(vi^2+2gh)

vf= root((5/root3)^2+2*9.8*10)

vf= 14.29 m/s

vf= 14.3 m/s

answer= b

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