MÜ06. Auto pidurdamine.

Ülesanne. Auto kiirus oli 82,8 km/h. Pärast pidurdamist peatus ta 7 s jooksul. Leida pidurdamisel läbitud teepikkus ja kiirendus.

Lahendus. Esmalt paneme kirja andmed.

Antud:

t equals 7 space s v subscript 0 equals 82 comma 8 space fraction numerator k m over denominator h end fraction equals 23 m over s minus negative negative negative negative negative negative negative negative negative negative negative a minus ? s minus ?

Saame leida alustuseks kiirenduse ning seejärel läbitud teepikkuse:

a equals fraction numerator v minus v subscript 0 over denominator t end fraction equals fraction numerator left parenthesis 0 minus 23 right parenthesis begin display style m over s end style over denominator 7 space s end fraction equals negative 23 over 7 m over s squared s equals s subscript 0 plus v subscript 0 times t plus fraction numerator a t squared over denominator 2 end fraction equals 0 space m plus 23 m over s times 7 space s plus fraction numerator negative begin display style 23 over 7 end style begin display style m over s squared end style times left parenthesis 7 space s right parenthesis squared over denominator 2 end fraction equals 80 comma 5 space m.

Teepikkuse saab leida ka keskmise kiiruse kaudu:

s equals v subscript k times t equals fraction numerator v plus v subscript 0 over denominator 2 end fraction times t equals fraction numerator left parenthesis 0 plus 23 right parenthesis begin display style m over s end style over denominator 2 end fraction times 7 space s equals 80 comma 5 space m

VASTUS: Auto kiirendus onnegative 23 over 7 m over s squared ning läbitud teepikkus 80 comma 5 space m.