An object moves in two ly9b ee ;1-xybdimensions according to $$\vec{r}(t)=(4.0t^{2}-9.0)\hat{i}+(2.0t-5.0)\hat{j}$$ where $r$ is in meters and $t$ in seconds. When does the object cross the x-axis?

  The graph shows velocity as a fw ydj*u tg*1:ounction of time for a car. What was the acceleration at y o:*w1gut *djtime $= 90$ seconds?

  The coordinate of an object is giq; d9a *a7eelcven as a function of time by $x=8t-3t^{2},$ where $x$ is in meters and $t$ is in seconds. Its average velocity over the interval from $t=1$ to $t=2\,\mathrm{s}$ is

  An object is released from rest and falgr;bvqjb myj4.ox 0nhn w5l.;2sxy u5k+2 + ajls a distance $h$ during the first second of time. How far will it fall during the next second of time?

  A crate of toys remains at resi*kk6bud1jsu y 1osvls/ 8.va c-e:*l v -on2jt on a sleigh as the sleigh is pulled up a hill with an increasing speed. The crate is not fastened down to the sleigh. What force is responsible for the cra 1y-s :ki./sj -6v*us2e*1bavu lvokn8ljdocte's increase in speed up the hill?

  At time $t=0$ a drag racer starts from rest at the origin and moves along a straight line with velocity given by $v=5t^{2}$, where $v$ is in $m/s$ and $t$ in $s$. The expression for the displacement of the car from $t=0$ to time $t$ is

  The chemical potential energy stored in a battgfgn9xk.hb b8 dj1,t5 ery is converted into kinetic enertkhgx f.9b5bj 8, gnd1gy in a toy car that increases its speed first from $0\,\mathrm{mph}$ to $2\,\mathrm{mph}$ and then from $2\,\mathrm{mph}$ up to $4\,\mathrm{mph}$. Ignore the energy transferred to thermal energy due to friction and air resistance. Compared to the energy required to go from $0$ to $2\,\mathrm{mph}$, the energy required to go from $2$ to $4\,\mathrm{mph}$ is

  When two stars are very far apart their gravi vvi/.6riwfgbd, -6 fmtational potential energy is zero; when they are separated by a distancedfm,66if vr igw.-/ bv $d$ the gravitational potential energy of the system is $U$. If the stars are separated by a distance $2d$ the gravitational potential energy of the system is

  A large wedge rests on a horizontal frictionl9wdweuv, /qd0 ess surface, as shown. A block starts from rest and slides down the inclined surface of the wedge, which is rough. During the motion of the block9wu/q0 dedw ,v, the center of mass of the block and wedge

  Two wheels with fixed : mjn2l+mjt 9 yh73 6evqboxi-hubs, each having a mass of $1\,\mathrm{kg}$, start from rest, and forces are applied as shown. Assume the hubs and spokes are massless, so that the rotational inertia is $I=mR^{2}$. In order to impart identical angular accelerations about their respective hubs, how large must $F_{2}$ be?

  A uniform disk, a thin hoop, and a uniform sphere, all with the same mass and s4d-u mz ty/nr mc7;k-58-bxqvyt aa z ixm::s6ame outer radius, are each free to rotate about a fixed axis through its center. Assume the hoop is connected to the rotation axis by light spokes. With the objects starting from rest, identical forces are simultaneously ap-kvdyt-:4nxymuz q/ a sr7z6i mb-m :;ta8c5xplied to the rims, as shown. Rank the objects according to their kinetic energies after a given time $t$, from least to greatest.

  A $2\,\mathrm{kg}$ rock is suspended by a massless string from one end of a uniform $1\,\mathrm{meter}$ measuring stick. What is the mass of the measuring stick if it is balanced by a support force at the $0.20\,\mathrm{meter}$ mark?

  A particle moves aloptu.zj)uu ;e/ng the x-axis. It collides elastically head-on with an identical parteu uzpj./t ;)uicle initially at rest. Which of the following graphs could illustrate the momentum of each particle as a function of time?

  When the speed of a rear-drive car ist8kzau 0il )i, increasing on a horizontal road, the direction of the frictional force on the )i0luk8i,a zt tires is

  A uniform disk ($I=\frac{1}{2}MR^{2}$) of mass $8.0\,\mathrm{kg}$ can rotate without friction on a fixed axis. A string is wrapped around its circumference and is attached to a $6.0\,\mathrm{kg}$ mass. The string does not slip. What is the tension in the cord while the mass is falling?

  A baseball is dropped on top of a basketball. The basketba.kh6 cu8d ,/i+cnamc ell hits the ground, reb uc8iea.nkcm,h/ d6c+ ounds with a speed of $4.0\,\mathrm{m/s}$, and collides with the baseball as it is moving downward at $4.0\,\mathrm{m/s}$. After the collision, the baseball moves upward as shown in the figure and the basketball is instantaneously at rest right after the collision. The mass of the baseball is $0.2\,\mathrm{kg}$ and the mass of the basketball is $0.5\,\mathrm{kg}$. Ignore air resistance and ignore any changes in velocities due to gravity during the very short collision times. The speed of the baseball right after colliding with the upward moving basketball is

  A small point-like object is thrown horizontallqn5ay*m *txlhs2m- w9pg) 2lj y off of a $50.0\,\mathrm{m}$ high building with an initial speed of $10.0\,\mathrm{m/s}$. At any point along the trajectory there is an acceleration component tangential to the trajectory and an acceleration component perpendicular to the trajectory. How many seconds after the object is thrown is the tangential component of the acceleration of the object equal to twice the perpendicular component of the acceleration of the object? Ignore air resistance.

  A small chunk of ice falls from rest down a frictionlesh*fsr 4-uzcm8 s parabolic ice sheet shown in the figure. At the point labeled A in the diagram, the ice sh84hfms-c uzr*eet becomes a steady, rough incline of angle $30^{\circ}$ with respect to the horizontal and friction coefficient $\mu_{k}$. This incline is of length $\frac{3}{2}h$ and ends at a cliff. The chunk of ice comes to rest precisely at the end of the incline. What is the coefficient of friction $\mu_{k}$?

  A non-Hookian spring has* e4w, lu:uuj xnl(n,o force $F=-kx^{2}$ where $k$ is the spring constant and $x$ is the displacement from its unstretched position. For the system shown of a mass $m$ connected to an unstretched spring initially at rest, how far does the spring extend before the system momentarily comes to rest? Assume that all surfaces are frictionless and that the pulley is frictionless as well.

  A point-like mass moves h49 vy fnel;fy9orizontally between two walls on a frictionless surface with initial kl4v9 y en;ffy9inetic energy $E$. With every collision with the walls, the mass loses $\frac{1}{2}$ its kinetic energy to thermal energy. How many collisions with the walls are necessary before the speed of the mass is reduced by a factor of 8?

  If the rotational inertia of a sphere about an axis throu(fdi:m :t(raeyp/52 +xvscz ogh the center of the sphere idaiosy:vtr( m+c ( x2fp5z/:es $I$, what is the rotational inertia of another sphere that has the same density, but has twice the radius?

  Two rockets are in space in a negligibl e 3vj2a8gz0ave gravitational field. All observations are made by an observer in a reference frame in which both rockets are initially at rest. The masses of the rockev3v ega8ja0z2ts are $m$ and $9m$. A constant force $F$ acts on the rocket of mass $m$ for a distance $d$. As a result, the rocket acquires a momentum $p$. If the same constant force $F$ acts on the rocket of mass $9m$ for the same distance $d$, how much momentum does the rocket of mass $9m$ acquire?

  If a planet of radiuke;;7*gclcx ls $R$ spins with an angular velocity $\omega$ about an axis through the North Pole, what is the ratio of the normal force experienced by a person at the equator to that experienced by a person at the North Pole? Assume a constant gravitational field $g$ and that both people are stationary relative to the planet and are at sea level.

  A ball of mass $m$ is launched into the air. Ignore air resistance, but assume that there is a wind that exerts a constant force $F_{o}$ in the $-x$ direction. In terms of $F_{0}$ and the acceleration due to gravity $g$, at what angle above the positive x-axis must the ball be launched in order to come back to the point from which it was launched?

  Find the period of small oscillations ofn xl*q1,( un*dzbnr9 ztr+pc7 a water pogo, which is a stick of mass r1dr(lq97+nzpt b,*nu*z n xc$m$ in the shape of a box (a rectangular parallelepiped.) The stick has a length $L$, a width $w$ and a height $h$ and is bobbing up and down in water of density $\rho$. Assume that the water pogo is oriented such that the length $L$ and width $w$ are horizontal at all times. Hint: The buoyant force on an object is given by $F_{buoy}=\rho Vg$, where $V$ is the volume of the medium displaced by the object and $\rho$ is the density of the medium. Assume that at equilibrium, the pogo is floating.

  A sled loaded with children starts from rest and slidesa w+:nrx ,bym h5b71pdui -wq3+j*dvz down a snowy $25^{\circ}$ (with respect to the horizontal) incline traveling 85 meters in 17 seconds. Ignore air resistance. What is the coefficient of kinetic friction between the sled and the slope?

  A space station consists of two living modules attached to a central hub otc k:qp0 tk0me9;6znrn opposite sides of the hub by long corridors of equal length. Each living module contains N astronauts of equal mass. The mass of the space station is negligible compared to the mass of the astronauts, and the size of the centrmen0tt9pk6;qr c 0 :kzal hub and living modules is negligible compared to the length of the corridors. At the beginning of the day, the space station is rotating so that the astronauts feel as if they are in a gravitational field of strength $g$. Two astronauts, one from each module, climb into the central hub, and the remaining astronauts now feel a gravitational field of strength $g^{\prime}$. What is the ratio $g^{\prime}/g$ in terms of N?

  A simplified model of a bicycle of mass M has two tisx)-a e0cvv7ook-t5 fres that each comes into contact with the ground at a point. The wheelbase of this bicycle (the distance between the points of contact with the ground) is w, and the center of mass of the bicycle is located midway between the tires and a height h above the ground. The bicycle is moving to the right, but slowing down at a constant rate. The acceleration has a magnitude a. Air resistance may be ignored. Assumxk-tvfv7 o)s0c-ae5 o e that the coefficient of sliding friction between each tire and the ground is $\mu$, and that both tires are skidding: sliding without rotating. What is the maximum value of $\mu$ so that both tires remain in contact with the ground?

  A simplified model of a bi+q qg avxbw*x8 ap *.p 8gy-mqev5;i/rcycle of mass M has two tires that each comes into contact with the ground at a point. The wheelbase of this bicycle (the distance between the points of contact with the ground) is w, and the center of mass of the bicycle p*qp8-5vx*ieb+y w qvm8a.xa;/ rgqgis located midway between the tires and a height h above the ground. The bicycle is moving to the right, but slowing down at a constant rate. The acceleration has a magnitude a. Air resistance may be ignored. Assume that the coefficient of sliding friction between each tire and the ground is $\mu$, and that both tires are skidding: sliding without rotating. What is the maximum value of $a$ so that both tires remain in contact with the ground?

  A simplified model of a bicycle of mass M has two tires that each y5pjfqp+)1djkbi mf 1 ,g 9cr.comes into contact with the ground at a point. The wheelbase of this bicycle (the distance between the points of contact with the ground) is w, and the center of mass of the bicycle is located midway between the tires and a height h above the ground. 5f)pm +pg.fqj9 j,y rd1i bk1cThe bicycle is moving to the right, but slowing down at a constant rate. The acceleration has a magnitude a. Air resistance may be ignored. Assume, instead, that the coefficient of sliding friction between each tire and the ground is different: $\mu_1$ for the front tire and $\mu_2$ for the rear tire. Let $\mu_1 = 2\mu_2$. Assume that both tires are skidding: sliding without rotating. What is the maximum value of $a$ so that both tires remain in contact with the ground?

  A thin, uniform rod has mass w5xuk0zwg26 q;c2g e4nv4v bx$m$ and length $L$. Let the acceleration due to gravity be $g$. Let the rotational inertia of the rod about its center be $md^{2}$. Find the ratio $L/d$.

  A thin, uniform rod hvy.v)3vu yh/,tf )snuas mass $m$ and length $L$. Let the acceleration due to gravity be $g$. Let the rotational inertia of the rod about its center be $md^{2}$. The rod is suspended from a point a distance $kd$ from the center, and undergoes small oscillations with an angular frequency $\beta\sqrt{\frac{g}{d}}$. Find an expression for $\beta$ in terms of $k$.

  A thin, uniform rod hasn scdsj )izbj21+s9rlx,eo/+ mass $m$ and length $L$. Let the acceleration due to gravity be $g$. Let the rotational inertia of the rod about its center be $md^{2}$. The rod is suspended from a point a distance $kd$ from the center, and undergoes small oscillations with an angular frequency $\beta\sqrt{\frac{g}{d}}$. Find the maximum value of $\beta$.

  A point object of mas3 bu; ls1m mt5oac*3uws $m$ is connected to a cylinder of radius $R$ via a massless rope. At time $t=0$ the object is moving with an initial velocity $v_{0}$ perpendicular to the rope, the rope has a length $L_{0},$ and the rope has a non-zero tension. All motion occurs on a horizontal frictionless surface. The cylinder remains stationary on the surface and does not rotate. The object moves in such a way that the rope slowly winds up around the cylinder. The rope will break when the tension exceeds $T_{max}$ Express your answers in terms of $T_{max}$ m, $L_{0},$ R, and $v_{0}$. What is the angular momentum of the object with respect to the axis of the cylinder at the instant that the rope breaks?

  A point object of ma 8yq:+ r6u irh/dsph.fss $m$ is connected to a cylinder of radius $R$ via a massless rope. At time $t=0$ the object is moving with an initial velocity $v_{0}$ perpendicular to the rope, the rope has a length $L_{0},$ and the rope has a non-zero tension. All motion occurs on a horizontal frictionless surface. The cylinder remains stationary on the surface and does not rotate. The object moves in such a way that the rope slowly winds up around the cylinder. The rope will break when the tension exceeds $T_{max}$ Express your answers in terms of $T_{max}$ m, $L_{0},$ R, and $v_{0}$. What is the kinetic energy of the object at the instant that the rope breaks?

  A point object of ma sl vv)+;dsv6( d2d ed.wxhla*ss $m$ is connected to a cylinder of radius $R$ via a massless rope. At time $t=0$ the object is moving with an initial velocity $v_{0}$ perpendicular to the rope, the rope has a length $L_{0},$ and the rope has a non-zero tension. All motion occurs on a horizontal frictionless surface. The cylinder remains stationary on the surface and does not rotate. The object moves in such a way that the rope slowly winds up around the cylinder. The rope will break when the tension exceeds $T_{max}$ Express your answers in terms of $T_{max}$ m, $L_{0},$ R, and $v_{0}$. What is the length (not yet wound) of the rope?

  A massless elastic cord ;iz6o7- xxr.k z.xj l(lxud;k (that obeys Hooke's Law) will break if the tension in the cord xz-lu6k.x.dzx7k (rxi ;j;l oexceeds $T_{max}$. One end of the cord is attached to a fixed point, the other is attached to an object of mass 3m. If a second, smaller object of mass $m$ moving at an initial speed $v_{0}$ strikes the larger mass and the two stick together, the cord will stretch and break, but the final kinetic energy of the two masses will be zero. If instead the two collide with a perfectly elastic one-dimensional collision, the cord will still break, and the larger mass will move off with a final speed of $v_{f}$. All motion occurs on a horizontal, frictionless surface. Find $v_{f}/v_{0}$

  A massless elastic cord (that obeys Hooke's L0hwzf8r15j r aqxl egsa+*8t,aw) will break if the tension in the cord 1a*a08jleg wh,t 5r+8fq xrzsexceeds $T_{max}$. One end of the cord is attached to a fixed point, the other is attached to an object of mass 3m. If a second, smaller object of mass $m$ moving at an initial speed $v_{0}$ strikes the larger mass and the two stick together, the cord will stretch and break, but the final kinetic energy of the two masses will be zero. If instead the two collide with a perfectly elastic one-dimensional collision, the cord will still break, and the larger mass will move off with a final speed of $v_{f}$. All motion occurs on a horizontal, frictionless surface. Find the ratio of the total kinetic energy of the system of two masses after the perfectly elastic collision and the cord has broken to the initial kinetic energy of the smaller mass prior to the collision.