Physics I Practice Problems For Dummies (+ Free Online Practice). Dummies Consumer

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       94. A swimmer can move at a speed of 2 meters per second in still water. If he attempts to swim straight across a 500-meter-wide river with a current of 8 meters per second parallel to the riverbank, how many meters will the swimmer traverse by the time he reaches the other side? Round your answer to the nearest tenth of a kilometer.

       95. A basketball rolling at a rate of 10 meters per second encounters a gravel patch that is 5 meters wide. If the basketball is moving in a direction 15 degrees north of east, and if the sides of the gravel patch are aligned parallel to the north-south axis, will the basketball still be rolling by the time it reaches the far side of the patch if the gravel gives it an acceleration of –3 meters per second squared in the same direction it started when it entered the patch? If so, what will be its speed in the easterly direction upon exiting the patch? If not, how many meters (measured perpendicularly to the western edge of the patch) will the basketball roll on the gravel before stopping? Round your numerical response to the nearest integer.

       96. Partway through a car trip, a dashboard compass stops working. At the time it broke, Bill had driven 180 kilometers in a direction 70 degrees north of west. He then proceeds to drive 45 kilometers due south on the highway, before turning right and driving 18 kilometers west on Sunset St. When he stops the car, how far is Bill from the location where he began the trip? Round your answer to the nearest kilometer.

Moving under the Influence of Gravity: Projectile Launched Horizontally

      97–99

       97. A marble rolls off a 2-meter-high, flat tabletop. In how many seconds will it hit the floor? Round your answer to the nearest tenth of a second.

       98. Mark rolls a boulder off a cliff located 22 meters above the beach. If he’s able to impart a velocity of 0.65 meters per second to the boulder, how many meters from the base of the cliff will the boulder land? Round your answer to the nearest tenth of a meter.

       99. A car flies off a flat embankment with a velocity of 132 kilometers per hour parallel to the ground 45 meters below. With what velocity does the car ultimately crash into the ground? Round your answer to the nearest meters per second.

Moving under the Influence of Gravity: Projectile Launched at an Angle

      100–105

       100. Alicia kicks a soccer ball with a velocity of 10 meters per second at a 60-degree angle relative to the ground. What is the horizontal component of the velocity? Round your answer to the nearest tenth of a meter per second.

       101. The punter for the San Diego Chargers kicks a football with an initial velocity of 18 meters per second at a 75-degree angle to the horizontal. What is the vertical component of the ball’s velocity at the zenith (highest point) of its path? Round your answer to the nearest tenth of a meter per second.

       102. A cannonball fired at a 20-degree angle to the horizontal travels with a speed of 25 meters per second. How many meters away does the cannonball land if it falls to the ground at the same height from which it launched? Round your answer to the nearest meter.

       103. Launching from a 100-meter-high ski jump of unknown inclination at 40 meters per second, an Olympic athlete grabs 8.2 seconds of hang time before landing on the ground. How far away from the jump does she land?

       104. A cannon tilted at an unknown angle fires a projectile 300 meters, landing 11 seconds after launch at a final height equal to its starting one. At what angle was the cannon fired?

       105. Will a baseball struck by a bat, giving the ball an initial velocity of 35 meters per second at 40 degrees to the horizontal, result in a home run if it must clear a 1.8-meter-high fence 120 meters away? If it will, by how many centimeters will the ball clear? If not, how many centimeters short will it be? Assume that the ball is struck at a height of 0.8 meters, and round your answer to the nearest 10 centimeters.

Chapter 4

      Pushing and Pulling: The Forces around You

      Newton’s laws of motion describe how objects move when forces are applied to them. The first law states that an object’s velocity won’t change unless you apply a force to it. One of the most famous and important equations in physics is Newton’s second law: Force equals mass times acceleration. The third law says that whenever you exert a force on an object, that object will exert an equal force on you.

       The Problems You’ll Work On

      In this chapter you’ll apply Newton’s laws to the following types of problems:

      ✓ Using Newton’s second law to relate force and acceleration

      ✓ Drawing free-body diagrams

      ✓ Determining equal and opposite forces with Newton’s third law

      ✓ Redirecting forces with pulleys

       What to Watch Out For

      You’ll be forced to try the problem again unless you keep the following in mind:

      ✓ Drawing a free-body diagram to make sure you include all the forces

      ✓ Determining the components of the forces on your free-body diagrams with the correct signs

      ✓ Remembering that the equal and opposite forces in Newton’s third law always act on different objects

      ✓ Recalling that the magnitude of the tension of a massless rope is the same all along the rope

Resisting Motion with Newton’s First Law

      106–107

       106. What are the SI units of mass?

       107. What property of an object does mass measure?

Forcing a Massive Object to Accelerate

      108–109

       108. What is the acceleration of a 0.25-kilogram particle subject to a single force of 10 newtons eastward?

       109. A 300-gram block slides across a ceramic floor at a speed of 13.5 meters per second. If no forces act on the block along the axis of its motion, what is the block’s speed 1 second later? Round your answer to the nearest tenth of a meter per second.

Drawing Free-Body Diagrams

      110–113 Use the following force diagram of a mass hanging from a pulley by a massless rope to answer Questions 110–113. Letters on the diagram signify vectors.

      Illustration by Thomson Digital

       110. Which vector represents the gravitational force Earth exerts on the mass?

       111. Which vector(s) represent the force of tension?

       112. Which two vectors always have equal magnitudes?

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