Question #236607

A car moves at a constant acceleration and crosses a path of 400m. What is the acceleration if the car takes 10 seconds to cross the third 100m path?

1
Expert's answer
2021-09-13T11:02:12-0400

let for point P middle of the 400m path\text{let for point } P \text{ middle of the 400m path}

x0=0;v0>0x_0= 0;v_0>0

s(t)=v0t+at22s(t) = v_0t +\frac{at^2}{2}

s(10)=100s(10)=100

s(10)=10v0+50as(10)=10v_0+50a

v0+5a10=0 (1)v_0+5a-10 = 0\ (1)

s1=v12v022as_1=\frac{v_1^2-v_0^2}{2a}

for s1=200( the car has reached the end of the 400m path):\text{for }s_1=200(\text{ the car has reached the end of the 400m path}):

v1=0v_1 = 0

200=v022a200=\frac{-v_0^2}{2a}


a=v02400a= -\frac{v_0^2}{400}

Substitute a into expression (1)\text{Substitute a into expression (1)}

v0v028010=0v_0-\frac{v_0^2}{80}-10 = 0

v0280v0+800=0v_0^2-80v_0+800 = 0

v0=11.72ms;a=v02400=0.34ms2v_0= 11.72\frac{m}{s}; a = -\frac{v_0^2}{400}= -0.34\frac{m}{s^2}

v0=68.28ms;a=v02400=11.6ms2v_0'= 68.28\frac{m}{s}; a = -\frac{v_0^2}{400}= -11.6\frac{m}{s^2}


Answer: 0.34ms2 or 11.6ms2\text{Answer: }-0.34\frac{m}{s^2} \ or\ -11.6\frac{m}{s^2}


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