physics exam 2

3.96 m/s2; 237.996 N

A planet has a mass of 5.56 × 1023 kg and a radius of 3.06 × 106 m. (a) What is the acceleration due to gravity on this planet? (b) How much would a 60.1-kg person weigh on this planet?

4000 m

A plane is traveling at 200 m/s following the arc of a vertical circle of radius R. At the top of its path, the passengers experience "weightlessness." To one significant figure, what is the value of R?

1021.2996 N; 892.84 N

A rescue helicopter is lifting a man (weight = 892.840574902822 N) from a capsized boat by means of a cable and harness. (a) What is the tension in the cable when the man is given an initial upward acceleration of 1.41 m/s2? (b) What is the tension during the remainder of the rescue when he is pulled upward at a constant velocity?

13.33 M/S2; 48.9 degrees

A rocket of mass 3.95 × 105 kg is in flight near earth's surface. Its thrust is directed at an angle of 66.2° above the horizontal and has a magnitude of 8.57 × 106 N. Find the (a) magnitude and (b) direction of the rocket's acceleration. Give the direction as an angle above the horizontal.

4 (look of homework 5 number 17)

A small cylinder rests on a circular turntable that is rotating clockwise at a constant speed. Which set of vectors gives the direction of the velocity v and acceleration a of the cylinder, and the net force ΣF that acts on it.

4 N

An object weighs 10 N on the earth's surface. What is the weight of the object on a planet that has one tenth the earth's mass and one half the earth's radius?

5.1 m/s2

At a playground, a child slides down a slide that makes a 42° angle with the horizontal direction. The coefficient of kinetic friction for the child sliding on the slide is 0.20. What is the magnitude of her acceleration during her sliding?

3704.4 N; 16.8 m/s

A "swing" ride at a carnival consists of chairs that are swung in a circle by 19.2 m cables attached to a vertical rotating pole, as the drawing shows. Suppose the total mass of a chair and its occupant is 189 kg. (a) Determine the tension in the cable attached to the chair. (b) Find the speed of the chair.

24 m/s

A 0.75-kg ball is attached to a 1.0-m rope and whirled in a vertical circle. The rope will break when the tension exceeds 450 N. What is the maximum speed the ball can have at the bottom of the circle without breaking the rope?

56 N

A 20.0-kg package is dropped from a high tower in still air and is "tracked" by a radar system. When the package is 25 m above the ground, the radar tracking indicates that its acceleration is 7.0 m/s2. Determine the force of air resistance on the package.

2728.18 N

A 219-kg log is pulled up a ramp by means of a rope that is parallel to the surface of the ramp. The ramp is inclined at 27.3° with respect to the horizontal. The coefficient of kinetic friction between the log and the ramp is 0.838, and the log has an acceleration of 0.665 m/s2. Find the tension in the rope.

-4 N

A 4-kg block and a 2-kg block can move on the horizontal frictionless surface. The blocks are accelerated by a +12-N force that pushes the larger block against the smaller one. Determine the force that the 2-kg block exerts on the 4-kg block.

less than 0.5, but greater than zero.

A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure. Complete the following statement: If the 4-kg block is to begin sliding, the coefficient of static friction between the 4-kg block and the surface must be

mg(1-sin theta)

A block is at rest on a rough inclined plane and is connected to an object with the same mass as shown. The rope may be considered massless; and the pulley may be considered frictionless. The coefficient of static friction between the block and the plane is µs; and the coefficient of kinetic friction is µ k . What is the magnitude of the static frictional force acting on the block?

5.8e-9 N

A bowling ball (mass = 4.6 kg, radius = 0.11 m) and a billiard ball (mass = 0.36 kg, radius = 0.028 m) may each be treated as uniform spheres. What is the magnitude of the maximum gravitational force that each can exert on the other?

2.23 m/s2

A car travels at a constant speed around a circular track whose radius is 3.31 km. The car goes once around the track in 242 s. What is the magnitude of the centripetal acceleration of the car?

0.30

A crate rests on the flatbed of a truck that is initially traveling at 15 m/s on a level road. The driver applies the brakes and the truck is brought to a halt in a distance of 38 m. If the deceleration of the truck is constant, what is the minimum coefficient of friction between the crate and the truck that is required to keep the crate from sliding?

10.496 seconds

A girl is sledding down a slope that is inclined at 30.0º with respect to the horizontal. The wind is aiding the motion by providing a steady force of 117. N that is parallel to the motion of the sled. The combined mass of the girl and the sled is 65.8 kg, and the coefficient of kinetic friction between the snow and the runners of the sled is 0.149. How much time is required for the sled to travel down a 298-m slope, starting from rest?

B,C,A

A heavy block is suspended from a ceiling using pulleys in three different ways, as shown in the drawings. Rank the tension in the rope that passes over the pulleys in ascending order (smallest first).

The elevator could be moving upward at constant speed.

A man stands on a spring scale in a moving elevator and notices that the scale reading is 20% larger than when he weighs himself in his bathroom. Which statement can not be true?

987.2 N; 908.516 N

A mountain climber, in the process of crossing between two cliffs by a rope, pauses to rest. She weighs 575 N. As the drawing shows, she is closer to the left cliff than to the right cliff, with the result that the tensions in the left and right sides of the rope are not the same. Find the tensions in the rope to the left and to the right of the mountain climber.

4.13e5 m/s

A neutron star has a mass of 2.0 × 1030 kg (about the mass of our sun) and a radius of 5.0 × 103 m (about the height of a good-sized mountain). Suppose an object falls from rest near the surface of such a star. How fast would this object be moving after it had fallen a distance of 0.016 m? (Assume that the gravitational force is constant over the distance of the fall and that the star is not rotating.)

3.466e8

A spacecraft is on a journey to the moon. At what point, as measured from the center of the earth, does the gravitational force exerted on the spacecraft by the earth balance that exerted by the moon? This point lies on a line between the centers of the earth and the moon. The distance between the earth and the moon is 3.85 × 108 m, and the mass of the earth is 81.4 times as great as that of the moon.

8.64 m/s

A student is skateboarding down a ramp that is 7.85 m long and inclined at 23.0° with respect to the horizontal. The initial speed of the skateboarder at the top of the ramp is 3.81 m/s. Neglect friction and find the speed at the bottom of the ramp.

35.9 N

A student presses a book between his hands, as the drawing indicates. The forces that he exerts on the front and back covers of the book are perpendicular to the book and are horizontal. The book weighs 32.2 N. The coefficient of static friction between his hands and the book is 0.449. To keep the book from falling, what is the magnitude of the minimum pressing force that each hand must exert?

0.0928

A toboggan slides down a hill and has a constant velocity. The angle of the hill is 5.30° with respect to the horizontal. What is the coefficient of kinetic friction between the surface of the hill and the toboggan?

630.4 N

A woman stands on a scale in a moving elevator. Her mass is 53.0 kg, and the combined mass of the elevator and scale is an additional 739 kg. Starting from rest, the elevator accelerates upward. During the acceleration, the hoisting cable applies a force of 9420 N. What does the scale read (in N) during the acceleration?

69.72 kg

A worker stands still on a roof sloped at an angle of 39° above the horizontal. He is prevented from slipping by a static frictional force of 430 N. Find the mass of the worker.

2.13 m

At an amusement park there is a ride in which cylindrically shaped chambers spin around a central axis. People sit in seats facing the axis, their backs against the outer wall. At one instant the outer wall moves at a speed of 3.51 m/s, and an 59.5-kg person feels a 344-N force pressing against his back. What is the radius of a chamber?

6.94 m/s2

Communication satellites are placed in a circular orbit that is 1.20 × 106 m above the surface of the earth. What is the magnitude of the acceleration due to gravity at this distance?

Newton's first law of motion is valid.

Complete the following statement: An inertial reference frame is one in which

996.98 n

For background pertinent to this problem, review Conceptual Example 6. In Figure 5.7 the man hanging upside down is holding a partner who weighs 657 N. Assume that the partner moves on a circle that has a radius of 3.68 m. At a swinging speed of 4.32 m/s, what force must the man apply to his partner in the straight-down position?

5.93 m/s

In an amusement park ride, a child stands against the wall of a cylindrical room that is then made to rotate. The floor drops downward and the child remains pinned against the wall. If the radius of the room is 2.15 m and the relevant coefficient of friction between the child and the wall is 0.600, with what minimum speed is the child moving if he is to remain pinned against the wall?

case 1

In which case will the magnitude of the normal force on the block be equal to (Mg + F sin θθ)?

0.319

Multiple-Concept Example 7 deals with the concepts that are important in this problem. A penny is placed at the outer edge of a disk (radius = 0.117 m) that rotates about an axis perpendicular to the plane of the disk at its center. The period of the rotation is 1.84 s. Find the minimum coefficient of friction necessary to allow the penny to rotate along with the disk.

15.023 m/s2; 56.3 degrees

Only two forces act on an object (mass = 4.80 kg), as in the drawing. Find the (a) magnitude and (b) direction (relative to the x axis) of the acceleration of the object.

168 N

Part (a) of the drawing shows a bucket of water suspended from the pulley of a well; the tension in the rope is 84.0 N. Part (b) shows the same bucket of water being pulled up from the well at a constant velocity. What is the tension in the rope in part (b)?

356.04 N

Refer to Concept Simulation 4.4 for background relating to this problem. The drawing shows a large cube (mass = 21.0 kg) being accelerated across a horizontal frictionless surface by a horizontal force P. A small cube (mass = 4.8 kg) is in contact with the front surface of the large cube and will slide downward unless P is sufficiently large. The coefficient of static friction between the cubes is 0.710. What is the smallest magnitude that P can have in order to keep the small cube from sliding downward?

0.694

Speedboat A negotiates a curve whose radius is 135 m. Speedboat B negotiates a curve whose radius is 280 m. Each boat experiences the same centripetal acceleration. What is the ratio vA/vB of the speeds of the boats?

68.7 N

The drawing shows box 1 resting on a table, with box 2 resting on top of box 1. A massless rope passes over a massless, frictionless pulley. One end of the rope is connected to box 2, and the other end is connected to box 3. The weights of the three boxes are W1 = 59.9 N, W2 = 34.6 N, and W3 = 25.8 N. Determine the magnitude of the normal force that the table exerts on box 1.

fs,A = fs,B = fs,C/2

The drawing shows three blocks, each with the same mass, stacked one upon the other. The bottom block rests on a frictionless horizontal surface and is being pulled by a force F→F→ that is parallel to this surface. The surfaces where the blocks touch each other have identical coefficients of static friction. Which one of the following correctly describes the magnitude of the net force of static friction fs that acts on each block?

6.0177e-5 N; 1.896e-5 N; -7.9137e-5

The drawing shows three particles far away from any other objects and located on a straight line. The masses of these particles are mA = 377 kg, mB = 542 kg, and mC = 127 kg. Take the positive direction to be to the right. Find the net gravitational force, including sign, acting on (a) particle A, (b) particle B, and (c) particle C.

463.97 m/s; 3.374e-2 m/s2; 259.466 m/s; 0.01887 m/s2

The earth rotates once per day about an axis passing through the north and south poles, an axis that is perpendicular to the plane of the equator. Assuming the earth is a sphere with a radius of 6.38 x 106 m, determine the speed and centripetal acceleration of a person situated (a) at the equator and (b) at a latitude of 56.0 ° north of the equator.

108.55 N; 50.14 N;

This force can either push the block upward at a constant velocity or allow it to slide downward at a constant velocity. The magnitude of the force is different in the two cases, while the directional angle θ is the same. Kinetic friction exists between the block and the wall, and the coefficient of kinetic friction is 0.320. The weight of the block is 45.0 N, and the directional angle for the force F→F→ is θ = 49.0°. Determine the magnitude of F→F→ when the block slides (a) up the wall and (b) down the wall.

90.56 N; 56.80 degrees

Three forces act on a moving object. One force has a magnitude of 75.8 N and is directed due north. Another has a magnitude of 49.6 N and is directed due west. What must be (a) the magnitude and (b) the direction of the third force, such that the object continues to move with a constant velocity? Express your answer as a positive angle south of east.

B, A, C

Three identical blocks are being pulled or pushed across a horizontal surface by a force F→F→, as shown in the drawings. The force F→F→ in each case has the same magnitude. Rank the kinetic frictional forces that act on the blocks in ascending order (smallest first).

2.508e-10 m/s2

Three uniform spheres are located at the corners of an equilateral triangle. Each side of the triangle has a length of 1.40 m. Two of the spheres have a mass of 4.26 kg each. The third sphere (mass unknown) is released from rest. Considering only the gravitational forces that the spheres exert on each other, what is the magnitude of the initial acceleration of the third sphere?

4.2 N; 5.6 N; 0.9767 m/s2; 0.6512 m/s2

Two blocks are sliding to the right across a horizontal surface, as the drawing shows. In Case A the mass of each block is m1 = m2 = 4.3 kg. In Case B the mass of block 1 (the block behind) is m1 = 8.6 kg, and the mass of block 2 is m2 = 4.3 kg. No frictional force acts on block 1 in either Case A or Case B. However, a kinetic frictional force of 8.4 N does act on block 2 in both cases and opposes the motion. For both Case A and Case B determine (a) the magnitude of the forces with which the blocks push against each other and (b) the magnitude of the acceleration of the blocks.

Car A is not accelerating, but car B is accelerating.

Two cars are traveling at the same constant speed v. Car A is moving along a straight section of the road, while B is rounding a circular turn. Which statement is true about the acceleration of the cars?

4.1 m/s2 at 52 degrees

Two forces act on a 16-kg object. The first force has a magnitude of 68 N and is directed 24° north of east. The second force is 32 N, 48° north of west. What is the acceleration of the object resulting from the application of these two forces to the object?

5.35 m/s2; 227.19 N

Two objects (51.0 and 15.0 kg) are connected by a massless string that passes over a massless, frictionless pulley. The pulley hangs from the ceiling. Find (a) the acceleration of the objects and (b) the tension in the string.

0.619 m/s2 due east; 0.8 m/s2 due west

Two skaters, a man and a woman, are standing on ice. Neglect any friction between the skate blades and the ice. The mass of the man is 84 kg, and the mass of the woman is 65 kg. The woman pushes on the man with a force of 52 N due east. Determine the acceleration (magnitude and direction) of (a) the man and (b) the woman.

0.33

Two sleds are hooked together in tandem as shown in the figure. The front sled is twice as massive as the rear sled.The sleds are pulled along a frictionless surface by an applied force F→F→. The tension in the rope between the sleds is T→T→.Determine the ratio of the magnitudes of the two forces, TFTF.

0.58 m/s2

When a parachute opens, the air exerts a large drag force on it. This upward force is initially greater than the weight of the sky diver and, thus, slows him down. Suppose the weight of the sky diver is 983 N and the drag force has a magnitude of 1041 N. The mass of the sky diver is 100 kg. Take upward to be the positive direction. What is his acceleration, including sign?

69.19 degrees

While moving in, a new homeowner is pushing a box across the floor at a constant velocity. The coefficient of kinetic friction between the box and the floor is 0.380. The pushing force is directed downward at an angle θ below the horizontal. When θ is greater than a certain value, it is not possible to move the box, no matter how large the pushing force is. Find that value of θ.