The force that keeps you from sljh j,*z s),l-sc (mo,gdmy7pyiding on an icy sidewalk is

  It's more difficult to start moving a heavy carton frpjsc*7i-0 r c nej,f1e/ ts0;epd,c*k 5fsyddom rest than it is to keep pushing it with const *yre ccs-fdck dps*/pjf;705t, ij, s nee01dant velocity, because

  A horizontal force accelerates a box from rest across a horw:dw1**eu 2nd 0+yqzn53arae gz:r mfizontal surface (frictionz+:3ndy12 :q nwuar0wa rf*5mgde*ez is present) at a constant rate. The experiment is repeated, and all conditions remain the same with the exception that the horizontal force is doubled. What happens to the box's acceleration?

  A packing crate slides down an inc ; :vxfcqp6n)21 tey nekj.o3b.r0t vblined ramp at constant velocity. Thus we can dedu .1ftq :benr3c xy; v0.6p)jvnboe2ktce that

  A block of mass M slides down a friction.4.zfjk t+y clless plane inclined at an angle q with the horizontal. The normal rztlkc+.4jy .feaction force exerted by the plane on the block is

  A block of mass M slides down a frictionless plane inclined at an angle 2hb ge- eh7n4-seila0q with the horizontal. The normal reeb l-7 nie4h0gesa2 -haction force exerted by the plane on the block is directed

  A block of mass M slides down a frictionless plane inclined at an angle q withlk1q ep1s8.d 2a sb xl+ bvlaujj/.3t. the horizontal. The gravitational2vs /l13ulsqe dbbjja1 +.k.a.p8x t l force is directed

  Two toy cars (33 kg and 9.3 kg) are released simultaneously on an inclinatv9t9ie h87z*1s hy med plane th i*hthzs9vaet 8 7y9m1at makes an angle of $30^{\circ}$ with the horizontal. Make a statement which best describes their acceleration after being released.

  A person of weight 699 N stands on ap i;g oh.wy ye*6qqwwwaf;bg91zs1;: scale in an elevator. What will the scale be reading when the elevator is accelerating downwar *61wpq 9 fqywa;:;ew1wg;b.oih yzsgd at $2 \; m/s^2$?

  A person on a scale rides in an elevator. If the mass of the person ea06+z u70rba+ev9i h budp l*is 60.0 kg and the elevator accelerate+ 9eurd+a0 pvb ubl ieh7za*60s downward with an acceleration of $4.90 \; m/s^2$, what is the reading on the scale?

  A person on a scale r3fo3qm35hy zah:j:auo/g/ 3gy uy- spides in an elevator. If the mass of the person is 78.2 kg and the elevator q:zgg yom3 3j/u:u -h3 sfypy/3ha oa5accelerates upward with an acceleration of $15.7 \; m/s^2$, what is the reading on the scale?

  In the Atwood machine shown in Fig. below, if M = +s mrxiecnc,0rc/7o*vkk +0t2.00 kg and m = 0.62 kg, what is th7mvinrt0sk*ckcr + 0c,e +/ xoe magnitude of the acceleration of the system? (Ignore friction and the mass of the pulley.)

  In the Atwood machine shown in Fig. below, if M = 0.60 kg and m = 0.40 kg, 9ll9 p2ahxt7 xwhat is the tension in the stxl9t9x7hl 2 apring? (Ignore friction and the mass of the pulley.)

  A student pulls a box of books on a smooth horizontal floor with ydfh2s uyhj. s czo9)mcls:2wt4l 8(8a force of 97 $N$ in a direction of $37^{\circ}$ above the horizontal. If the mass of the box and the books is 32 kg, what is the acceleration of the box?

  A student pulls a box of boo 7*f *zgq,-xa0grtq gtks on a smooth horizontal floor with a force of 100 N in a direction ofr7*0 ,gtgqa*tg-f zxq $37.0^{\circ}$ above the horizontal. If the mass of the box and the books is 40.0 kg, what is the normal force on the box?

  A traffic light of weia0 agg(7:vlvlght 100 N is supported by two ropes as shown in Fig. below. What are the tensions aa:l(v7gvl0gin the ropes?

  In Fig. below, if the tensions in the ropes are 61b g*rm:5hi(lltjk(7 w(rd bk 0 $N$, what is the mass of the traffic light?

  Two boxes of masses m and 2m are in contact with each other on a fricf:qd+x2 o vn1 kmarf01tionless surq1:2 k0vxfonr dam+f1 face. (See Fig. below) What is the acceleration of the more massive box?

  Two boxes of masses m and 2m are in contact with each othzi /:m-j ggjnqff6zqhf,d6 y b5(0n.ter on a frictionless surface. (6tz, i5gy fzq bh/qj:g-(d mfnf.jn 60See Fig. below) What is the net force on the more massive box?

  Two boxes of masses m an) +;ro vft.nmyd 2m are connected by a rope. (See Fig. below) If the forward force on the more massive box is F, what is the tension in the connecrtf+v );no. ymting rope?

  Two boxes of masses m b,v odw;qrp1 3qpg(o (and 2m are connected by a rope. (See Fig. below) If the forward force on the more mass p1ogq(,; pb3dv rq(owive box is F, what is the acceleration of the less massive box?

  Two boxes are connected by a cord running over a pulley as shown in Fig. belrgnuwln 7z0d v xjkf9+)x7 k+4ow Box I of mass 9.1 kg rest on the top of dnxzxul ++ 0vj) 7gf9n7rkw4kthe table; the coefficient of kinetic friction between box I and the table is 0.10. Box II has a mass of 15.0 kg.
(a) Calculate the acceleration of the system  (数值)  $m/s^2$
(b) Calculate the tension in the cord  (数值)  $N$

  The coefficient of static and kinetic frictions between a 3.0-kg box and a desk tb: q:) zgo63ijzdnjn,i 67kuare 0.40 and jzujiq)6 d og:itn n:3b7, 6kz0.30, respectively. What is the net force on the box when a 15 N horizontal force is applied to the box?

  The coefficients of static and kinetic fmrivlv2+7z2xd5* 8nxa*i v h erictions for plastic on wood are 0.48 and l8avi d75 nz *xr*i+v2v2mhxe0.33,
respectively. How much horizontal force would you need to apply to a 13.9 N plastic calculator to start it moving from rest?

  An object slides on a level surface in the +x direction. It slows pgf+,wd dy-jd2uz o17bl3f6 7fx.pz fand comes to a stop with a constant acceleruj.xdpd3gbzf61yow7f d-2z fp + 7f ,lation of -$6.01 \; m/s^2$. What is the coefficient of kinetic friction between the object and the floor?

  A 10-kg box sitting on a horizontal surface is puls5nonyfw e76h z a63k:opi*a 7led by a 8.7 $N$ force. A 2.0 $N$ friction force retards the motion. What is the acceleration of the object?

  A horizontal force of 5.0 N accelerates a 4.0-kg mass, from restxsr+(pa5 fb0j y .wx.s, at a rate of $0.50 \; m/s^2$ in the positive direction. What friction force acts on the mass?

  During a hockey game, a puck is given an ini y3 (gxych yd5hc;1ht9tial speed of 10 m/s. It slides 50 m5cxgdc1h t; 3yhhy(9 y on the ice before it stops. What is the coefficient of kinetic friction between the puck and the ice?

  During the investigation of a traffici +xt47 zpbyd z*9mm77no pds9 accident, police find skid marks 90.0 m long. They determine the coefficient of friction between the car's tires and the ronbi79* +97zt4ddo xppsm mzy7adway to be 0.500 for the prevailing conditions. Estimate the speed of the car when the brakes were applied.

  Two boxes of masses m and 3m llwl/)t6)rzwl(wvp9 are stacked. (See Fig. below) The surface between the more massive box and the horizontal surface is smooth and the surface between the boxes is rough. If the less massive box does not slide on the more massive box, what is the static lwp )wtl)/v6l(rzl9w friction force on the less massive box?

  Two boxes of masses m and 1+nt t*2lpqge qj-:we 3m are stacked. (See Fig. below) The surface between th w:e1-+nqqjte p*l 2gte more massive box and the horizontal surface is smooth and the surface between the boxes is rough. If the less massive box does not slide on the more massive box, what is the coefficient of static friction between the boxes?

  An object is on a frictionless inclined plane. The plane is inclik h*u5(qh9ze tned at an angle of (qhh*ze5t ku9$18^{\circ}$ with the horizontal. What is the object's acceleration?

  A 10-kg mass slides down a flat hill that makes;m:+v ne ti5xtt8l)ds an angle of $10^{\circ}$ with the horizontal. If friction is negligible, what is the resultant force on the sled?

  A mass is placed on a smooth inclined plane with an angl9jztg+6g f4vtu -y5q oe of $37^{\circ}$ to the horizontal. If the inclined plane is 5.0-m long, how long does it take for the mass to reach the bottom of the inclined plane after it is released from rest?

A block lies on a smooth inclined plane tyv-f2 nb.sd. (3 hua;vz3jzxkilted at an angle of $35^{\circ}$ to the horizontal.
(a) Draw the free-body diagram for the block.
(b) Determine the block's acceleration as it slides down the inclined plane.
(c) If the block started from rest 8.5 m up the incline from its base, determine the block's speed when it reaches the bottom of the incline.
(d) How long did it take the block to reach the bottom of the inclined plane?

  A wooden block slides directly doww kzpnqo2bth7528)mdw2 stf( n an inclined plane, at a constant velocity offb2wk h5dnm8z ()t s2t7po2wq 2.5 m/s.
What is the coefficient of kinetic friction, if the plane makes an angle of $16^{\circ}$ with the horizontal?

  An object with a mass m slidmh o(0 ix4ue4des down a rough $37^{\circ}$ inclined plane where the coefficient of kinetic friction is 0.20. What is the acceleration of the object?

  An object with a mass m slides down 4g x(o7gsbibp*ivs;1 a rough $37^{\circ}$ inclined plane where the coefficient of kinetic friction is 0.14. If the plane is 10 m long and the mass starts from rest, what will be its speed (m/s) at the bottom of the plane?

  A bulldozer drags a l4d.nbpbw)j 8f dkq8z7 og weighing 500 N along a rough surface. The cable attached to the log makew 788b.bqpjd 4 kz)dfns an angle of $30.0^{\circ}$ with the ground. The coefficient of static friction between the log and the ground is 0.500. What minimum tension is required in the cable in order for the log to begin to move?

A 25.0-kg box is releasedr n u(,ysb2,x1oak: jjg vam;5(vz d0b from rest on a rough inclined plane tilted at an angle 2kzog;ja vbj1,nm b(:5vx, a( d0 syruof $33.5^{\circ}$ to the horizontal. The coefficient of kinetic friction between the box and the inclined plane is 0.200.
(a) Draw the free-body diagram for the box.
(b) Determine the force of kinetic friction acting on the box.
(c) Determine the acceleration of the box as it slides down the inclined plane.

  An object is placed on ax s +)0j7xelulja /jd,2xraf5n inclined plane. The angle of incline is gradually increased until the object begins to slide. The angle at which this occurs is q. What is the coefficiejjjx25fx/ r s 0,7eulada)x+lnt of static friction between the object and the plane?