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HW 3
1)
A car traveling at 69 km/h hits a bridge abutment. A passenger in the car moves forward a
distance of 57 cm (with respect to the road) while being brought to rest by an inflated air bag.
What magnitude of force (assumed constant) acts on the passenger’s upper torso, which has
a mass of 39 kg?
2)
A car that weighs 1.4 × 10
4
N is initially moving at a speed of 35 km/h when the brakes are
applied and the car is brought to a stop in 18 m. Assuming that the force that stops the car is
constant, find the magnitude of that force.
Find the time required for the change in speed.
If the initial speed is, instead, twice as great, and the car experiences the same force during
the braking, how is the stopping distance changed?
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View Full DocumentHow is the stopping time changed? (There could be a lesson here about the danger of driving
at high speeds.)
3) A certain force gives mass m
1
an acceleration of 12.5 m/s
2
and mass m an acceleration of 3.8 m/s
2
.
What acceleration would the force give to an object with a mass of (m
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 '11
 DR.STELIOSKAPRANIDIS
 Physics, Force

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