let for point P middle of the 400m path
x0=0;v0>0
s(t)=v0t+2at2
s(10)=100
s(10)=10v0+50a
v0+5a−10=0 (1)
s1=2av12−v02
for s1=200( the car has reached the end of the 400m path):
v1=0
200=2a−v02
a=−400v02
Substitute a into expression (1)
v0−80v02−10=0
v02−80v0+800=0
v0=11.72sm;a=−400v02=−0.34s2m
v0′=68.28sm;a=−400v02=−11.6s2m
Answer: −0.34s2m or −11.6s2m
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