Grav and Energy Practice APMultiple ChoiceIdentify the choice that best completes the statement or answers the question.____1.The unit of work, joule, is dimensionally the same as:a.newton/second.b.newton/kilogram.c.newton-second.d.newton-meter.____2.A worker pushes a sled with a force of 40 N over a level distance of 6.0 m. If a frictional force of 24 N acts on the wheelbarrow in a direction opposite to that of the worker, what net work is done on the wheelbarrow?a.240 Jb.216 Jc.144 Jd.96 J____3.What is the kinetic energy of a 0.135-kg baseball thrown at 40.0 m/s (90.0 mph)?a.54.0 Jb.87.0 Jc.108 Jd.216 J____4.A horizontal force of 200 N is applied to a 55-kg cart across a 10-m level surface. If the cart accelerates at 2.0 m/s2, then what is the work done by the force of friction as it acts to retard the motion of the cart?a.-1 100 Jb.-900 Jc.-800 Jd.-700 J____5.If both mass and velocity of a ball are tripled, the kinetic energy is increased by a factor of:a.3.b.6.c.9.d.27.____6.A very light cart holding a 300-N box is moved at constant velocity across a 15-m level surface. What is the net work done in the process?a.zerob.1/20 Jc.20 Jd.2 000 J____7.When an object is dropped from a tower, what is the effect of the air resistance as it falls?a.does positive workb.increases the object's kinetic energyc.increases the object's potential energyd.None of the above choices are valid.____8.Samantha pushes a 50-N crate up a ramp 25.0 m in length and inclined at 10 with the horizontal. What potential energy change does the crate experience?a.13 Jb.55 Jc.120 Jd.220 J____9.A baseball catcher puts on an exhibition by catching a 0.15-kg ball dropped from a helicopter at a height of 101 m. What is the speed of the ball just before it hits the catcher's glove 1.0 m above the ground? (g = 9.8 m/s2 and ignore air resistance)a.44 m/sb.38 m/sc.31 m/sd.22 m/s____10.A 2.00-kg ball has zero potential and kinetic energy. Maria drops the ball into a 10.0-m-deep well. After the ball comes to a stop in the mud, the sum of its potential and kinetic energy is:a.zero.b.196 J.c.-196 J.d.392 J.____11.An 80 000-kg airliner is flying at 900 km/h at a height of 10.0 km. What is its total energy (kinetic + potential) if the total was 0 when the airliner was at rest on the ground?a.250 MJb.478 MJc.773 MJd.10 300 MJ____12.A 2 000-kg ore car rolls 50.0 m down a frictionless 10.0 incline. If there is a horizontal spring at the end of the incline, what spring constant is required to stop the ore car in a distance of 1.00 m?a.340 kN/mb.681 kN/mc.980 kN/md.1 960 kN/m____13.By how much is the energy stored in a Hooke's law spring increased when its stretch is increased from 8.00 cm to 16.0 cm?a.100%b.200%c.300 %d.The correct answer is not given.____14.A Hooke's law spring is mounted horizontally over a frictionless surface. The spring is then compressed a distance d and is used to launch a mass m along the frictionless surface. What compression of the spring would result in the mass attaining double the kinetic energy received in the above situation?a.1.41 db.1.73 dc.2.00 dd.4.00 d____15.Preston pushes a wheelbarrow weighing 500 N to the top of a 50.0-m ramp, inclined at 20.0 with the horizontal, and leaves it. Tamara accidentally bumps the wheelbarrow. It slides back down the ramp, during which an 80.0-N frictional force acts on it over the 50.0 m. What is the wheelbarrow's kinetic energy at the bottom at of the ramp? (g = 9.8 m/s2)a.4 550 Jb.6 550 Jc.8 150 Jd.13 100 J____16.A pile driver drives a post into the ground. The mass of the pile driver is 2 500 kg and it is dropped through a height of 8.0 m on each stroke. If the resisting force of the ground is 4.0 106 N, how far is the post driven in on each stroke?a.4.9 cmb.9.8 cmc.16 cmd.49 cm____17.A parachutist of mass 50.0 kg jumps out of an airplane at a height of 1 000 m. The parachute deploys, and she lands on the ground with a speed of 5.0 m/s. How much energy was lost to air friction during this jump?a.49 400 Jb.98 700 Jc.198 000 Jd.489 000 J____18.A Hooke's law spring is compressed a distance d and is used to launch a particle of mass m vertically to a height h above its starting position. Under double the compression, the spring is now used to launch a particle of mass 2 m. How high does the second mass rise above its starting position?a.hb.2 hc.3 hd.4 h____19.A force of 100 N is applied to a 50-kg mass in the direction of motion for a distance of 6.0 m and then the force is increased to 150 N for the next 4.0 m. For the 10 m of travel, how much work is done by the varying force?a.1 200 Jb.1 500 Jc.2 400 Jd.-1 500 J____20.Is it possible for the total mechanical energy of a moving particle to be negative?a.No, because a moving particle has positive kinetic energy.b.No, because potential energy cannot have a value more negative than the value of the positive kinetic energy of the particle.c.Only if friction is involved.d.yes____21.Three different mass projectiles are launched from the top of a building each at different angles of elevation. Each particle has the same initial kinetic energy. Which particle has the greatest speed just as it impacts with the ground?a.The one launched at the highest angle of elevation.b.The one with the highest mass.c.The one with the lowest mass.d.They all will have the same speed on impact.____22.A 0.12-m-radius grinding wheel takes 5.5 s to speed up from 2.0 rad/s to 11.0 rad/s. What is the wheel's average angular acceleration?a.9.6 rad/s2b.4.8 rad/s2c.1.6 rad/s2d.0.33 rad/s2____23.Somewhere between the Earth and the Moon is a point where the gravitational attraction of the Earth is canceled by the gravitational pull of the Moon. The mass of the Moon is 1/81 that of the Earth. How far from the center of the Earth is this point?a.8/9 the way to the Moonb.9/10 the way to the Moonc.3/4 the way to the Moond.80/81 the way to the Moon____24.A careful photographic survey of Jupiter's moon Io by the spacecraft Voyager 1 showed active volcanoes spewing liquid sulfur to heights of 70 km above the surface of this moon. If the value of g on Io is 2.0 m/s2, estimate the speed with which the liquid sulfur left the volcano.a.260 m/sb.530 m/sc.790 m/sd.970 m/s____25.Two satellites are monitored as they orbit the Earth; satellite X is eight times as far from the Earth's center as is satellite Y. From Kepler's third law one may conclude that the period or revolution of X is what factor times that of Y?a.1/2b.2.0c.4.0d.22.6____26.An asteroid in orbit about the sun has a linear speed of 4 km/s when at a distance of closest approach d from the sun. What is its linear speed when it is at its greatest distance from the sun, a distance 2 d?a.1 km/sb.2 km/sc.8 km/sd.16 km/s____27.Doubling the mean distance from the Sun results in changing the orbital period of revolution by what factor?a.21/2b.2c.23/2d.22____28.A car is going around a racetrack at constant speed. The curves around the track have different radii. In which turn is the magnitude of the car's acceleration the greatest?a.It is the greatest in the turn with the greatest radius.b.It is the greatest in the turn with the smallest radius.c.The acceleration is zero everywhere because of the constant speed.d.More information is needed to determine the answer.____29.A stunt pilot weighing 0.70 kN performs a vertical circular dive of radius 0.80 km. At the bottom of the dive, the pilot has a speed of 0.20 km/s which at that instant is not changing. What force does the plane exert on the pilot?a.3.6 kN upb.4.3 kN upc.2.9 kN downd.2.9 kN upe.5.8 kN down____30.A car travels around an unbanked highway curve (radius 0.15 km) at a constant speed of 25 m/s. What is the magnitude of the resultant force acting on the driver, who weighs 0.80 kN?a.0.87 kNb.0.34 kNc.0.80 kNd.0.00 kNe.0.67 kN____31.A 0.50 kg mass attached to the end of a string swings in a vertical circle (radius = 2.0 m). When the mass is at the highest point of the circle the speed of the mass is 8.0 m/s. What is the magnitude of the force of the string on the mass at this position?a.21 Nb.11 Nc.16 Nd.26 Ne.36 N____32.A 4.0-kg mass attached to the end of a string swings in a vertical circle of radius 2.0 m. When the string makes an angle of 35 with the vertical as shown, the speed of the mass is 5.0 m/s. At this instant what is the magnitude of the force the string exerts on the mass?a.50 Nb.82 Nc.89 Nd.11 Ne.61 N____33.An iceboat is traveling in a circle on the ice. Halfway around the circle the sail and the steering mechanism fall off the boat. Which statement is correct?a.The boat will continue traveling in the circle because there is no friction.b.The boat will continue to travel in the circle because its velocity exerts a force on it.c.The boat will move off on a line tangent to the circle because there is no force on it.d.The boat will move off tangent to the circle because there is a force on it perpendicular to the boat directed to the outside of the circle.e.The boat will move off to the outside perpendicular to the tangent line since a force directed to the outside of the circle always acts on the boat.____34.A hornet circles around a pop can at increasing speed while flying in a path with a 12-cm diameter. We can conclude that the hornet's wings must push on the air with force components that area.straight down.b.down and inwards.c.down and outwards.d.down and backwards.e.down, backwards and outwards.____35.A car enters a level, unbanked semi-circular hairpin turn of 100 m radius at a speed of 28 m/s. The coefficient of friction between the tires and the road is m = 0.800. If the car maintains a constant speed of 28 m/s, it willa.attempt to dig into the road surface.b.tend to veer toward the center of the semicircle.c.arrive safely at the end of the semicircle.d.tend to veer toward the outside of the circle.e.veer toward the center for the first quarter-circle, then veer toward the outside for the second quarter-circle.____36.If a dense 20.0-kg object is falling in air at half its terminal velocity, what is the drag force on the object at this moment?a.24.5 Nb.49.0 Nc.69.3 Nd.98.0 Ne.139 N____37.A body moving along the x axis is acted upon by a force Fx that varies with x as shown. How much work is done by this force as the object moves from x = 1 m to x = 8 m?a.-2 Jb.-18 Jc.-10 Jd.-26 Je.+18 J____38.When a ball rises vertically to a height h and returns to its original point of projection, the work done by the gravitational force isa.0.b.-mgh.c.+mgh.d.-2mgh.e.+2mgh.____39.Equal amounts of work are performed on two bodies, A and B, initially at rest, and of masses M and 2M respectively. The relation between their speeds immediately after the work has been done on them isa.vA = vB.b.vA = 2vB.c.vA = vB.d.vB = vA.e.vB = 2vA.____40.If the scalar (dot) product of two vectors is negative, it means thata.there was a calculator error.b.the angle between the vectors is less than 90 degrees.c.the angle between the vectors is 90 degrees.d.the angle between the vectors is greater than 270 degrees.e.the angle between the vectors is between 90 and 180 degrees.____41.Negative work can be donea.by friction on the tires while a car is accelerating without skidding.b.by a spring at the bottom of an elevator shaft when it stops a falling elevator.c.by a hand catching a ball.d.by all of the above.e.only by (b) and (c) above.____42.A moving particle is subject to conservative forces only. When its kinetic energy decreases by 10 J, what happens to its mechanical energy?a.It increases by 10 J.b.It decreases by 10 J.c.It increases, but not necessarily by 10 J.d.It decreases, but not necessarily by 10 J.e.It remains the same.____43.A pendulum is made by letting a 2.0-kg object swing at the end of a string that has a length of 1.5 m. The maximum angle the string makes with the vertical as the pendulum swings is 30. What is the speed of the object at the lowest point in its trajectory?a.2.0 m/sb.2.2 m/sc.2.5 m/sd.2.7 m/se.3.1 m/s____44.A spring (k = 600 N/m) is placed in a vertical position with its lower end supported by a horizontal surface. The upper end is depressed 20 cm, and a 4.0-kg block is placed on top of the depressed spring. The system is then released from rest. How far above the point of release will the block rise?a.46 cmb.36 cmc.41 cmd.31 cme.20 cm____45.A spring (k = 600 N/m) is at the bottom of a frictionless plane that makes an angle of 30 with the horizontal. The upper end of the spring is depressed 0.10 m, and a 2.0-kg block is placed against the depressed spring. The system is then released from rest. What is the kinetic energy of the block at the instant it has traveled 0.10 m and the spring has returned to its uncompressed length?a.2.0 Jb.1.8 Jc.2.2 Jd.1.6 Je.1.0 J____46.A 0.75-kg sphere is released from rest and is moving 5.0 m/s after falling 2.0 m in a viscous medium. What is the change in mechanical energy caused by the force the viscous medium exerts on the sphere during this descent?a.-6.1 Jb.-4.6 Jc.-5.3 Jd.-6.8 Je.-2.7 J____47.A 1.2-kg mass is projected up a rough circular track (radius = 0.80 m) as shown. The speed of the mass at point A is 8.4 m/s, and at point B, it is 5.6 m/s. What is the change in mechanical energy between A and B caused by the force of friction?a.-2.7 Jb.-8.8 Jc.-4.7 Jd.-6.7 Je.-19 J____48.Cubical blocks of mass m and side l are piled up in a vertical column. The total gravitational potential energy of a column of three blocks isa.mgl.b.3mgl.c.mgl.d.6mgl.e.9mgl.____49.A pendulum bob has potential energy U0 when held taut in a horizontal position. The bob falls until it is 30 away from the horizontal position, when it has potential energy UA. It continues to fall until the string is vertical, when it has potential energy UB. Compare its potential energies at O, A, and B.a.U0 = UA = UB.b.UA - UB = 2U0.c.UA - UB = U0 - UA.d.U0 = UB = 2UA.e.U0 - UA = 2(UA - UB).____50.A spring with spring constant k = 800 N/m is compressed 12 cm from its equilibrium position. A spring with spring constant k = 400 N/m has the same elastic potential energy as the first spring when its extension isa.0.060 m.b.0.085 m.c.0.12 m.d.0.17 m.e.0.24 m.____51.A spring with spring constant k = 800 N/m is extended 12 cm from its equilibrium position. A spring with 6.0 cm extension from equilibrium will have the same potential energy as the first spring if its spring constant isa.200 N/m.b.400 N/m.c.800 N/m.d.1 600 N/m.e.3 200 N/m.____52.As an object moves from point A to point B only two forces act on it: one force is nonconservative and does -30 J of work, the other force is conservative and does +50 J of work. Between A and B,a.the kinetic energy of object increases, mechanical energy decreases.b.the kinetic energy of object decreases, mechanical energy decreases.c.the kinetic energy of object decreases, mechanical energy increases.d.the kinetic energy of object increases, mechanical energy increases.e.None of the above.____53.As an object moves from point A to point B only two forces act on it: one force is conservative and does -70 J of work, the other force is nonconservative and does +50 J of work. Between A and B,a.the kinetic energy of object increases, mechanical energy increases.b.the kinetic energy of object decreases, mechanical energy increases.c.the kinetic energy of object decreases, mechanical energy decreases.d.the kinetic energy of object increases, mechanical energy decreases.e.None of the above.____54.A 3.50 kg block is pulled along a moving conveyor belt at a constant speed of 0.500 m/s relative to a stationary observer while the belt moves at a constant speed of 0.200 m/s in the opposite direction. If the coefficient of kinetic friction is 0.400, the magnitude of the mechanical energy dissipated, in J, caused by the force of friction on the block in 8.00 s isa.5.6.b.22.0.c.32.9.d.54.8.e.76.8.Problem55.A sample of blood is placed into a centrifuge of radius 15.0 cm. The mass of a red corpuscle is 3.0 10-16 kg, and the centripetal force required to make it settle out of the plasma is 4.0 10-11 N. At how many revolutions per second should the centrifuge be operated?56.A space station in the form of a large wheel, 120 m in diameter, rotates to provide an "artificial gravity" of 3.00 m/s2 for persons located at the outer rim. Find the rotational frequency of the wheel (in revolutions per minute) that will produce this effect.57.An airplane pilot experiences weightlessness as she passes over the top of a loop-the-loop maneuver. If her speed is 200 m/s at the time, find the radius of the loop.58.A race car starts from rest on a circular track of radius 400 m. Its speed increases at the constant rate of 0.500 m/s2. At the point where the magnitudes of the radial and tangential accelerations are equal, determine (a) the speed of the race car, and (b) the elapsed time.59.A baseball outfielder throws a baseball of mass 0.15 kg at a speed of 40 m/s and initial angle of 30. What is the kinetic energy of the baseball at the highest point of the trajectory?60.A surprising demonstration involves dropping an egg from a third-floor window to land on a foam-rubber pad 2 in (5 cm) thick without breaking. If a 56-gram egg falls 12 m, and the foam pad stops the egg in 6.25 ms, by how much is the pad compressed?61.A simple pendulum, 2.0 m in length, is released from rest when the support string is at an angle of 25 from the vertical. What is the speed of the suspended mass at the bottom of the swing?62.When an automobile moves with constant velocity the power developed is used to overcome the frictional forces exerted by the air and the road. If the power developed in an engine is 50.0 hp, what total frictional force acts on the car at 55 mph (24.6 m/s)? One horsepower equals 746 W.