Physics Questions & Answers
- Verify the answer to Example 8.11 by: (a) finding the angular displacement of the wheel using equations for constant α; (b) finding the change in rotational kinetic energy of the wheel; and (c) finding the torque from W = τΔ Example... Posted 3 months ago
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- Find the force exerted by the same person’s deltoid muscle when holding a 1.0 L juice carton (weight 9.9 N) with the arm outstretched and parallel to the floor (as in Fig. 8.31). Assume that the juice carton is 60.0 cm from the shoulder. Posted 3 months ago
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- A uniform ladder of mass 10.0 kg and length 3.2 m leans against a frictionless wall with its base located 1.5 m from the wall. If the ladder is not to slip, what must be the minimum coefficient of static friction between the bottom of the ladder and... Posted one year ago
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- A uniform diving board of length 5.0 m is supported at two points; one support is located 3.4 m from the end of the board and the second is at 4.6 m from the end (Fig. 8.19). The supports exert vertical forces on the diving board. A diver stands at... Posted one year ago
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- Is it possible for the net torque on an object to be zero and the net force nonzero? Is it possible for the net force to be zero and the net torque nonzero? Posted 4 months ago
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- A person is lying on an exercise mat and lifts one leg at an angle of 30.0° from the horizontal with an 89 N (20 lb) weight attached to the ankle (Fig. 8.15). The distance between the ankle weight and the hip joint (which is the rotation axis... Posted one year ago
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- Figure 8.7 shows a modified form of Atwood’s machine where one of the blocks slides on a table instead of hanging from the pulley. The blocks are released from rest. Find the speed of the blocks after they have moved a distance h in terms of 1... Posted 4 months ago
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- A playground merry-go-round is essentially a uniform disk that rotates about a vertical axis through its center (Fig. 8.5). Suppose the disk has a radius of 2.0 m and a mass of 160 kg; a child of mass 18.4 kg sits at the edge of the merry-go-round.... Posted 2 years ago
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- A 0.122 kg dart is fired from a gun with a speed of 132 m/s horizontally into a 5.00 kg wooden block. The block is attached to a spring with a spring constant of 8.56 N/m. The coefficient of kinetic friction between the block and the horizontal... Posted 3 months ago
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- Two pendulum bobs have equal masses and lengths (5.1 m). Bob A is initially held horizontally while bob B hangs vertically at rest. Bob A is released and col-lides elastically with bob B. How fast is bob B moving immediately after the collision? Posted one year ago
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- A boy of mass 60 kg is sledding down a 70 m slope starting from rest. The slope is angled at 15° below the horizontal. After going 20 m along the slope, he passes his friend, who hops onto the sled. The friend has a mass of 50 kg, and the... Posted 10 months ago
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- A Vulcan spaceship has a mass of 65 000 kg and a Romulan spaceship is twice as massive. Both have engines that generate the same total force of 9.5 × 10 6 N. (a) If each spaceship fires its engine for the same amount of time, starting from rest,... Posted 3 months ago
- At the beginning of a scene in an action movie, the 78.0 kg star, Indianapolis Jones, stands on a ledge 3.70 m above the ground and the 55.0 kg heroine, Georgia Smith, stands on the ground. Jones swings down on a rope, grabs Smith around the waist,... Posted 3 months ago
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- Pendulum bob A has half the mass of pendulum bob B. Each bob is tied to a string that is 5.1 m long. When bob A is held with its string horizontal and then released, it swings down and, once bob A’s string is vertical, it collides elastically... Posted 3 months ago
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- Gerald wants to know how fast he can throw a ball, so he hangs a 2.30 kg target on a rope from a tree. He picks up a 0.50 kg ball of putty and throws it horizontally against the target. The putty sticks to the target and the putty and target swing up... Posted 10 months ago
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- In Example 7.8, suppose instead that the fragment of mass 2M/3 has zero velocity immediately after the ex-plosion. Where does the other fragment land? Example 7.8 interval. From the impulse-momentum theorem [Eq. (7-8)], the momentum change of the... Posted 3 months ago
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- An object of mass 2.0 kg (the “projectile”) approaches a stationary object (the “target”) at 8.0 m/s. The projectile is deflected through an angle of 90.0° and its speed after the collision is 6.0 m/s. What is the speed... Posted 4 months ago
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- A child places 12 wooden blocks together, as shown in the figure. If each block has the same mass and density, where is the cm of these blocks? Each block is a cube with sides of 1.0 inch length. The origin of the coordinate system is at the center... Posted 10 months ago
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- A uniform rod of length 30.0 cm is bent into the shape of an inverted U. Each of the three sides is of length 10.0cm. Find the location, in x- and y-coordinates, of the cm as measured from the origin. Posted 10 months ago
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- A sled of mass 5.0 kg is coasting along on a frictionless ice-covered lake at a constant speed of 1.0 m/s. A 1.0 kg book is dropped vertically onto the sled. At what speed does the sled move once the book is on it? An automobile weighing 13.6kN is... Posted 5 months ago
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- A man with a mass of 65 kg skis down a frictionless hill that is 5.0 m high. At the bottom of the hill the terrain levels out. As the man reaches the horizontal section, he grabs a 20 kg backpack and skis off a 2.0 m high ledge. At what horizontal... Posted 3 months ago
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- Jane is sitting on a chair with her lower leg at a 30.0° angle with respect to the vertical, as shown. You need to develop a computer model of her leg to assist in some medical research. If you assume that her leg can be modeled as two uniform... Posted one year ago
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- In a game of pool, suppose that the cue ball initially moves in the −x-direction. After a collision with the 4-ball of equal mass, the cue ball moves at 52.0° above the −x-axis and the 4-ball moves at 38.0° below the... Posted 10 months ago
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- In a circus trapeze act, two acrobats fly through the air and grab on to each other, then together grab a swinging bar. One acrobat, with a mass of 60 kg, is moving at 3.0m/s at an angle of 10° above the horizontal, and the other, with a... Posted 4 months ago
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- A block of mass 2.00 kg slides eastward along a frictionless surface with a speed of 2.70 m/s. A chunk of clay with a mass of 1.50 kg slides southward on the same surface with a speed of 3.20 m/s. The two objects collide and move off together. What... Posted 3 months ago
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- (a) In Practice Problem 7.11, find the momentum change of the ball of mass 1 during the collision. Give your answer in x- and y-component form; express the components in terms of 1 and i . (b) Repeat for the ball of mass 2 . How are the momentum... Posted 3 months ago
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See AlsoState of the Union Address eBook - Use the result of Problem 58 to show that in any elastic head-on collision between two objects, the relative speed of the two is the same before and after the collision. A firecracker is tossed straight up into the air. It explodes into three pieces... Posted 3 months ago
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- A 0.010 kg bullet traveling horizontally at 400.0 m/s strikes a 4.0 kg block of wood sitting at the edge of a table. The bullet is lodged into the wood. If the table height is 1.2 m, how far from the table does the block hit the floor? A 6.0 kg... Posted 10 months ago
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- An object of 1.0 kg mass approaches a stationary object of 5.0 kg at 10.0 m/s and, after colliding, rebounds in the reverse direction along the same line with a speed of 5.0 m/s. What is the speed of the 5.0 kg object after the collision? A 2.0 kg... Posted 3 months ago
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- A 2.0 kg block is moving to the right at 1.0 m/s just before it strikes and sticks to a 1.0 kg block initially at rest. What is the total momentum of the two blocks after the collision? A 75 kg man is at rest on ice skates. A 0.20 kg ball is thrown... Posted 10 months ago
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- A 0.020 kg bullet traveling at 200.0 m/s east hits a motionless 2.0 kg block and bounces off it, retracing its original path with a velocity of 100.0 m/s west. What is the final velocity of the block? Assume the block rests on a frictionless... Posted one year ago
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- A helium atom (mass 4.00 u) moving at 618 m/s to the right collides with an oxygen molecule (mass 32.0 u) moving in the same direction at 412 m/s. After the collision, the oxygen molecule moves at 456 m/s to the right. What is the velocity of the... Posted 11 months ago
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- Consider two falling objects. Their masses are 3.0 kg and 4.0 kg. At time = 0, the two are released from rest. What is the velocity of their cm at = 10.0 s? Ignore air resistance. Object A of mass 3 kg is moving in the +x-direction with a... Posted 10 months ago
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- Belinda needs to find the cm of a sculpture she has made so that it will hang in a gallery correctly. The sculpture is all in one plane and consists of various shaped uniform objects with masses and sizes as shown. Where is the cm of this sculpture?... Posted 10 months ago
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- The positions of three objects, written as (x, y) coordinates, are: (1.0 m, 1.0 m), (2.0 m, 3.0 m), and (3.0 m, 1.0 m). The objects have equal masses. If one of the objects is moved 12 cm in the positive x-direction, by how much does the cm move? The... Posted one year ago
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- In an action movie, the hero dangles his archenemy over the edge of a cliff. The archenemy’s mass is 68 kg and his center of mass is 44 cm horizontally past the edge of the cliff. The hero’s center of mass is 15 cm horizontally from the... Posted 3 months ago
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- Women often experience back pain when they are pregnant. Suppose a woman’s mass before pregnancy is 68 kg and her center of mass when standing is located directly above the hips. By the thirty-fourth week of pregnancy, she has gained 8.0 kg... Posted 10 months ago
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- Particle A is at the origin and has a mass of 30.0 g. Particle B has a mass of 10.0 g. Where must particle B be located if the coordinates of the cm are (x, y) = (2.0 cm, 5.0 cm)? Particle A has a mass of 5.0 g and particle B has a mass of 1.0 g.... Posted one year ago
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- A marksman standing on a motionless railroad car fires a gun into the air at an angle of 30.0° from the horizontal. The bullet has a speed of 173 m/s (relative to the ground) and a mass of 0.010 kg. The man and car move to the left at a speed of... Posted 4 months ago
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- A cannon on a railroad car is facing in a direction parallel to the tracks. It fires a 98 kg shell at a speed of 105 m/s (relative to the ground) at an angle of 60.0° above the horizontal. If the cannon plus car have a mass of 5.0 × 10 4... Posted 10 months ago
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- A uranium nucleus (mass 238 u), initially at rest, under-goes radioactive decay. After an alpha particle (mass 4.0u) is emitted, the remaining nucleus is thorium (mass 234 u). If the alpha particle is moving at 0.050times the speed of... Posted 10 months ago
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- Diana is standing on a raft of mass 100.0 kg that is floating on a still lake. She decides to walk the length of the raft. If Diana’s mass is 55 kg and she walks with a velocity of 0.91 m/s with respect to the shore, how fast and in what... Posted 3 months ago
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- A boy of mass 60.0 kg is rescued from a hotel fire by leaping into a firefighters’ net. The window from which he leapt was 8.0 m above the net. The firefighters lower their arms as he lands in the net so that he is brought to a complete stop in... Posted 4 months ago
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- A 3.0 kg object is initially moving northward at 15 m/s. Then a force of 15 N, toward the east, acts on it for 4.0s. (a) At the end of the 4.0 s, what is the object’s final velocity? (b) What is the change in momentum during the 4.0 s? A... Posted 10 months ago
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- For a safe reentry into Earth’s atmosphere, the pilots of a space capsule must reduce their speed from 2.6 × 10 4 m/s to 1.1 × 10 4 m/s. The rocket engine produces a backward force on the capsule of 1.8 × 10 5 N. The mass of the... Posted 10 months ago
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- A bird (mass 31 g) is flying at 11.1 m/s when it flies into a glass window and bounces off at a speed of 4.1 m/s. The bird is in contact with the glass for 0.071 s. What is the average force on the bird during the collision? An automobile traveling... Posted one year ago
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- Five cars are traveling on a highway. Their masses and initial speeds are: (a) 1500 kg, 30 m/s (b) 1500 kg, 20 m/s (c) 1000 kg, 30 m/s (d) 1000 kg, 20 m/s (e) 2000 kg, 40 m/s The cars use the same braking force to slow down and stop. Rank the cars in... Posted 3 months ago
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- Dynamite is being used to blast through rock to build a road. After one explosion, the masses and kinetic energies of several fragments of rock thrown up into the air are: (a) 8 kg, 400 J (b) 2 kg, 1600 J (c) 4 kg, 1600 J (d) 16 kg, 100 J (e) 1 kg,... Posted 11 months ago
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- An object of mass 3.0 kg is projected into the air at a 55° angle. It hits the ground 3.4 s later. What is its change in momentum while it is in the air? Ignore air resistance. A ball of mass 5.0 kg moving with a speed of 2.0 m/s in the... Posted 10 months ago
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- At = 0, six birds are flying south at 10 m/s. Their masses and their velocities at a later time are: (a) 200 g, 10 m/s north at = 30 s (b) 200 g, 10 m/s east at = 30 s (c) 200 g, 20 m/s north at = 60 s (d) 400 g, 20 m/s north... Posted 3 months ago
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- A system consists of three particles with these masses and velocities: mass 3.0 kg, moving north at 3.0 m/s; mass 4.0 kg, moving south at 5.0 m/s; and mass 7.0 kg, moving north at 2.0 m/s. What is the total momentum of the system? A sports car... Posted 10 months ago
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