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Answers
Answer:
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Answer:
Given ,
u= 10 m/s, a= g= -10 m/s²,s= - 40 m
By second equation of motion,
S= ut+1/2at²
Or-40= 10*t+ 1/2*-10*t²
Or, 5t²-10t-40= 0
Or,t²-2t-8= 0
Or, t²-4t+2t-8=0
Or,t(t-4)+2(t-4)=0
Or,(t-4)(t+2)=0
By zero product rule,
t-4=0. t-2=0
Or, t=4 Or,t=-2.
Since time cannot be negative, t= 4 seconds.
While returning from the highest point , u= 0, total height travelled= 5+40= 45m.
By the third equation of motion,
V²=u²+2gh
Or, v= √ 0+2*10*45
Or, v= √ 900
Or, v= 30 m/s
Distance covered by ball in the course of the journey:
V²=u²-2gh
Or, h=u²/2g( at highest point,v=0)
Or, h=100/2*10
Or, h= 5 m
Hence , total distance= 2*5 = 10 m
Hence, average speed= total distance/total time = 10/4=2.5 m/s.
Total Displacement of the ball= 10-40=-30 m
Hence, average velocity= total Displacement/ total time= -30/4= - 7.5 m/s = 7.5 m/s in opposite direction.