Question #8f009

2 Answers
Feb 9, 2015

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We need to find R which is given by R=#U_x#T

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

Using constant acceleration linear equations;

#g=(V_y-U_y)/T# and #h_y=((U_y+V_y)/2)T#
Substitute 1st equation into the second one to eliminate #V_y#;
#h_y=(2U_y+gT)T/2# and rearrange it to get a quadratic equation,
#gT^2+2U_yT-2h_y=0#

#g=9.81ms^-1, 2U_y=2xx15sin(20)ms^-1, 2h_y=2xx28m#

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

Now #R=U_xT=15cos(20)xx1.923m#
#R=27.1m#