In the figures shown, three particles are thrown from a tower of height 40m as shown in figure. In each case find the time when the particles strike the ground and the distance of this point from foot of tower.
A
5.46s,2.83s,1.46s,109.2m,56.6m,29.2m
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B
5.46s,1.46s,2.83s,109.2m,56.6m,29.2m
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C
1.46s,109.2m,56.6m,29.2m,5.46s,2.83s
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D
56.6m,29.2m,5.46s,2.83s,1.46s,109.2m
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Solution
The correct option is A5.46s,2.83s,1.46s,109.2m,56.6m,29.2m For the case (I),
Horizontal component of velocity=vx=20m/s
Vertical component of velocity=vy=20m/s
For the vertical motion,
s=vyt+12at2
⟹−40=20t−5t2
⟹t=5.46s
Thus the horizontal distance of point from the point of projection =vxt=109.2m
For the case (II),
Horizontal component of velocity=vx=20m/s
Vertical component of velocity=vy=0m/s
For the vertical motion,
s=vyt+12at2
⟹−40=−5t2
⟹t=2.83s
Thus the horizontal distance of point from the point of projection =vxt=56.6m
For the case (III),
Horizontal component of velocity=vx=20m/s
Vertical component of velocity=vy=−20m/s
For the vertical motion,
s=vyt+12at2
⟹−40=−20t−5t2
⟹t=1.46s
Thus the horizontal distance of point from the point of projection =vxt=29.2m