A car is traveling along a straight road at a velocity of +36.0m/s when its engine cuts out. For the next twelve seconds the carslows down, and its average acceleration is abar1. For the next 6seconds the car slows down further, and its average acceleration is abar2. Thevelocity of the car at the end of theeighteen-second period is +28.0 m/s. The ratio of the averageacceleration values is abar1/abar2 = 1.50. Find the velocity of thecar at the end of theinitial twelve-second interval.

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A car is traveling along a road, and its engine is turning overwith an angular velocity of +209 rad/s. The driver steps on theaccelerator, and in a time of 15.9 s the angular velocity increasesto +300 rad/s. (a) What would have been the angular displacement ofthe engine if its angular velocity had remained constant at theinitial value of +209 rad/s during the entire 15.9-s interval? (b)What would have been the angular displacement if the angularvelocity had been equal to its final value of +300 rad/s during theentire 15.9-s interval? (c) Determine the actual value of theangular displacement during the 15.9-s interval.
(a) ? = ? rad
(b) ? = ? rad
(c) ? = ? rad

vf = vi + at
rx = vit + Â½ at2
vf2 = vi2 +2arx
rx = Â½ (vi + vf)t

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23. The city is trying to figure out how long the traffic lightshould stay yellow at an intersection. The speed limit on the roadis 45.0 km/h and the intersection is 23.0 m wide. A car istraveling at the speed limit in the positive direction and canbrake with an acceleration of -5.20 m/s2. (a) If the car is to stopon the white line, before entering the intersection, what is theminimum distance from the line at which the driver must apply thebrakes?

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) Ion Rocket Engine. A special type of rocket engine useselectricity for propulsion: the ion engine. A soft metal, such ascesium, is vaporized and then electrified (ionized) with highvoltage. These cesium ions are the accelerated by strong electricfields to produce a current of atoms at high velocity. Outside theengine, the ions are then recombined with electrons to restoreelectrical neutrality.

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q) Kinetic Energy 1. A car has a mass of 1200 kg. How much kineticenergy does it have when traveling at a speed of 30 m/sec?

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Kinetic Energy 2. The Space Shuttle orbits the Earth at a speed ofsome 7750 meters per second (which is about 260 times that of atypical highway driving speed). With a typical payload, the Shuttlehas a mass of 120,000 kg.

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q-8
Mass of Earthâs Atmosphere. The pressure of the Earthâs atmosphereat sea level is 101,300 Pascals (Newtons per square meter.) Thismeans that every square meter of Earthâs surface supports a weightof 101,300 Newtons. From this, determine the mass of Earthâsatmosphere. What fraction of the Earthâs total mass is this?

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