(1) v=−9.8t+29.4v = -9.8t + 29.4v=−9.8t+29.4 h=−4.9t2+29.4th = -4.9t^2 + 29.4th=−4.9t2+29.4t (2) v=0v = 0v=0 のとき t=3t = 3t=3 これから h=−4.9⋅9+29.4⋅3=44.1h = -4.9 \cdot 9 + 29.4 \cdot 3 = 44.1h=−4.9⋅9+29.4⋅3=44.1 よって ３秒 44.1m (3) h=0h = 0h=0 のとき −t(4.9t−29.4)=0-t(4.9t - 29.4) = 0−t(4.9t−29.4)=0 t=0,6t = 0, 6t=0,6 t>0t > 0t>0 より t=6t = 6t=6 これから v=−9.8⋅6+29.4=−29.4v = -9.8 \cdot 6 + 29.4 = -29.4v=−9.8⋅6+29.4=−29.4 よって ６秒 −29.4-29.4−29.4m/s