When it crashes into a bridge support that does not move, a car goes from 100 km

Question

When it crashes into a bridge support that does not move, a car goes from 100 km/h to 0 in 1.23 m.

Part A

What is the impulse delivered to the 70-kg driver by the seat belt, assuming the belt makes the driver's motion identical to the car's motion? Assume that the initial direction of motion of the car is the positive direction.

Express your answer to two significant figures and include the appropriate units.

J=?

Part B

What is the average force exerted by the belt on the driver?

Express your answer to two significant figures and include the appropriate units.

Fav=?

Part C

If the driver were not wearing the seat belt and flew forward until he hit the steering wheel, which stopped him in 0.0145 s, what would be the average force exerted by the steering wheel on him?

Express your answer to two significant figures and include the appropriate units.

Fav=?

Explanation / Answer

convert the speed into m/s,

V=100*5/18=27.77 m/s

a)the impulse delivered to the driver by the seat belt= Delta (mV)

=m Delta(V)

=70(0-27.77)

=-1944.44 Kg.m/s

---------------------------------------------------------------------------------------------------------

b) from work energy theorem

F*D=0-1/2mV^2

F*1.23=0-1/2*70*(27.77)^2

F=1580.8 N

--------------------------------------------------------------------------------------

c) F=change in momentum/(time)

=Delta (mV)/t

=-1944.44 Kg.m/s/0.0145 s

F=-134099.31 N

Related Questions

Navigate

• Browse (All)
• Browse W
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.