Question #8f009

2 Answers
Feb 9, 2015

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We need to find R which is given by R=UxT

However, we need to find time of flight, T.

Using constant acceleration linear equations;

g=VyUyT and hy=(Uy+Vy2)T
Substitute 1st equation into the second one to eliminate Vy;
hy=(2Uy+gT)T2 and rearrange it to get a quadratic equation,
gT2+2UyT2hy=0

g=9.81ms1,2Uy=2×15sin(20)ms1,2hy=2×28m

You will get T=1.923s (take the positive one).

Now R=UxT=15cos(20)×1.923m
R=27.1m