A brick is thrown upward from the top of a building at an angle of 25° to the horizontal and with an initial speed of 15m/s. If the brick is in the flightfor 3.0 s, how tall is the building?
2 answers
https://www.jiskha.com/questions/682094/A-brick-is-thrown-upward-from-the-top-of-a-building-at-an-angle-of-25-to-the-horizontal
Vo = 15m/s[25o],
Yo = 15*sin25 = 6.3 m/s. = Ver. component of initial velocity.
Y = Yo + g*Tr = 0,
6.3 + (-9.8)Tr = 0,
Tr = 0.65 s. = Rise time.
Tr + Tf = 3 s,
0.65 + Tf = 3,
Tf = 2.35 s. = Fall time.
ho = 0.5g*Tf^2 = 4.9 * 2.35^2 = 27.1 m. above gnd.
Y^2 = Yo^2 + 2g*h = 0,
6.3^2 + (-19.6)h = 0,
h = 2.03 m. above the bldg.
hb + h = ho,
hb + 2.03 = 27.1,
hb = 25.1 m. = Ht. of the bldg.
Yo = 15*sin25 = 6.3 m/s. = Ver. component of initial velocity.
Y = Yo + g*Tr = 0,
6.3 + (-9.8)Tr = 0,
Tr = 0.65 s. = Rise time.
Tr + Tf = 3 s,
0.65 + Tf = 3,
Tf = 2.35 s. = Fall time.
ho = 0.5g*Tf^2 = 4.9 * 2.35^2 = 27.1 m. above gnd.
Y^2 = Yo^2 + 2g*h = 0,
6.3^2 + (-19.6)h = 0,
h = 2.03 m. above the bldg.
hb + h = ho,
hb + 2.03 = 27.1,
hb = 25.1 m. = Ht. of the bldg.
2 answers