The force that keeps you frs+o +/af ls bu8tq63utom sliding on an icy sidewalk is

  It's more difficult to spr .8 ai3zp ilew.j b;pqp0q;ca7v/m,tart moving a heavy carton from rest than it is to keep pushing q ;im3pvz8 l a0crp;p /ja,pbiqe..w7 it with constant velocity, because

  A horizontal force accelerates a box from rest across a ho;/w*5:wivruxnf3zfv - ;,u))e xyj4uvi gsk qrizontal surface (friction 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 :4 wu/x-kf;eq ni )v)u*gxjr ;svuf5iyv,z 3 wto the box's acceleration?

  A packing crate slides down an d t/uwtyz;tam3m.9,o inclined ramp at constant velocity. Thus we can deduce tha,;amu.tzt o /3dt w9myt

  A block of mass M slides down a frictionless plane inclined at an angle bfgo3ua)8f*, k)tzme+lzas9 j(se p7 q with the horizonta(e3oz 8 bm *)f +zk7stlfuj,)apgsa 9el. The normal reaction force exerted by the plane on the block is

  A block of mass M slides down a f ug52fdm k*w+ f4zx9bprictionless plane inclined at an angle q with the horizontal. The normal reaction force exertepz5mbwd*+f 4xgfk 9u2 d by the plane on the block is directed

  A block of mass M slides down a frictionless plane inclined at an angle q 3pcqw 2jrl01)hpu2 qg with the horizontal. puqqw1hg cp)l2r3j 20The gravitational force is directed

  Two toy cars (29 kg and 7.3 kg) are released simultanj v21qbnf(z(c eously on an inclined plane th1b z2 qfvn(j(cat makes an angle of $30^{\circ}$ with the horizontal. Make a statement which best describes their acceleration after being released.

  A person of weight 577 N stands on a scale in an elevator. What will the scale obk2 dp2c.8dvbbp2k dd82v c.oe reading when the elevator is accelerating downward at $2 \; m/s^2$?

  A person on a scale rides uskeu+p.m.ql . nh;tvr/ ++anin an elevator. If the mass of the person is 60.0 kg and the elevator accelerates downward wnh kn++.t. +u .vle; mqu/rpasith an acceleration of $4.90 \; m/s^2$, what is the reading on the scale?

  A person on a scale rides in an elevator. gj 41h09lz) f-ctbgh ctcjh;p* +u 6co If the mass of the person is 74.7 kg and go1hhjb+-pu04gj c6f9l cc*)c;tzh tthe elevator accelerates upward with an acceleration of $7.7 \; m/s^2$, what is the reading on the scale?

  In the Atwood machine shown in Fig. belaal *uc+by;e6vx (1s now, if M = 1.57 kg and m = 0.50 kg, what is the magnitude of the acceleratioucnvle 6a1+ ys(* ab;xn of the system? (Ignore friction and the mass of the pulley.)

  In the Atwood machine shown in Fig. belog1/, - vd g)a)+nx-; m-rohcscgzagoa w, if M = 0.60 kg and m = 0.40 kg, what is the tenrm-acc z; -gnxodv o)/- g)1 gasagh+,sion in the string? (Ignore friction and the mass of the pulley.)

  A student pulls a box of books on a smooth horizontal ffq9(j l3v hnx b.h(;urloor with a force of 42 $N$ in a direction of $37^{\circ}$ above the horizontal. If the mass of the box and the books is 58 kg, what is the acceleration of the box?

  A student pulls a box of books on a smooth horizontal floor with a forclz3hoar-ecz-/ 9oe( u u f1-kne of 100 N in a direction 9ue(k z/e1luonrzfhco-3a -- of $37.0^{\circ}$ 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 weight 100 N is supported by two ropes as shown in jhlkmwlp9p j;2,u(7e q *tnw, Fig. below. What are the tensejjl,pl ,nuw *wt9m;k p27h(qions in the ropes?

  In Fig. below, if the tensions in thubbub r9i1m bdez7j h5(/j-nsx; s 8glf3vi1 :e ropes are 21 $N$, what is the mass of the traffic light?

  Two boxes of masses m and 2m are in contact n rah/8mqz+7nqy:jj 4 with each other on a frictionless surface. 4 /q7h8a n+yrqznj: jm (See Fig. below) What is the acceleration of the more massive box?

  Two boxes of masses m and 2m are in contact wi+ch d. 82cvu*qs 31/f6pc lm,pruh tgbth each other on a frictionless surface. (See Fig. below) What is the net force on the more massc,cc.dv6 /phf bgu*smq2 tu3p rh+8l1ive box?

  Two boxes of masses m and 2m are connected b9x8 bw7xarhvolo 3+v+y a rope. (See Fig. below) If the forward force on the morx o+xvahv3brw 89 7l+oe massive box is F, what is the tension in the connecting rope?

  Two boxes of masses m and 2m are connected by a rope. ft n3vf2(3(-bpdp l nj (See Fig. below) If the forward force on the more massive box is F, what is the acceleration of the (2(tpvb3pdf3- nfln j less massive box?

  Two boxes are connected by a cord running over a pulley as 1-m xmhl)3y juj7a.oly 4c5lzshown in Fig. below Box I of mass 9.2 kg rest on the top of the table; the coefficient of kinetic friction between box I and the table is 0.10. Box II has a may4 -lc51.olxjhj mlu3az)m7y ss of 13.1 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 des)e fy9j 2+fmje+xs z6dk are 0.40 and 0.30, respectively. What is the net force on the 92dfxe yej6)+z ms+fj box when a 15 N horizontal force is applied to the box?

  The coefficients of statiece6okbogsc1+d77nzl ( 8 y/lc and kinetic frictions for plastic on wood are 0.47 and 0.30,7(8 c+1yce7 /zlodn6egb l sok
respectively. How much horizontal force would you need to apply to a 8.5 N plastic calculator to start it moving from rest?

  An object slides on a level surface in the +x h;4wr9 yutt.r direction. It slows and comes to a stop w uyh4;wt r9tr.ith a constant acceleration of -$3.56 \; m/s^2$. What is the coefficient of kinetic friction between the object and the floor?

  A 10-kg box sitting on a horizontal surface is pulled by6whc+1lm e4k x a 5.4 $N$ force. A 2.1 $N$ friction force retards the motion. What is the acceleration of the object?

  A horizontal force of 5.0 N mp;v)zjckz)w- 4wz ;r accelerates a 4.0-kg mass, from rest, 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 puz , fa)fixf9 jy+iz9+g0(m gbz*ceq 6ick is given an initial speed of 10 m/s. It slides 50 m on the ice before it stops. What is the coefficient of kinetic friction between the puck and m ,jz eiqc*aiy)gffg 6zibf+x 0 (9+z9the ice?

  During the investigation of a traffic accident, police fi9-w5b*hne k ehf9x3fpnd skid marks 90.0 m long. They determine the coefficient of friction between the car's tires and the roadway to be 0.500 for the prkeb fh9 5*fhn -p3wex9evailing conditions. Estimate the speed of the car when the brakes were applied.

  Two boxes of masses m and 3m are stacked. (See Fig. below) The .0 * aro, z(ew3b+ivqp(lk qjfsurface 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 frlpabw0 zkr*+3vi. e,(j(o qfqiction force on the less massive box?

  Two boxes of masses m and 3m are stacked.ro 7i jom805b7aa+hcq (See Fig. below) The surface between the more massive box and the horizontal surface is smooth and the surfai+07rhma5o q8 c7boj ace 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 frictiu jt7:yg h8fu 4/c)iwtonless inclined plane. The plane is inclined at an angle o f :8hwi74uctgut)y j/f $12^{\circ}$ with the horizontal. What is the object's acceleration?

  A 10-kg mass slides down a flat h oh4skfmv tcb usng bw/k:8gg q0829++ill that makes 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 yr7(a:t;s)kt d3 rewp plane with an angle 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 tilted at an angle hx2kc0j; 3 huwof $35^{\circ}$ 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 down an inclined plane, at a constant vel +o ,kg y-nzuq)d(+epiocity of 2.8 m/) o+dpi,yz-+geq(u nks.
What is the coefficient of kinetic friction, if the plane makes an angle of $14^{\circ}$ with the horizontal?

  An object with a mass m slides down a rou48/3iy;zpcx .r jwceugh $37^{\circ}$ inclined plane where the coefficient of kinetic friction is 0.20. What is the acceleration of the object?

  An object with a mass m slinqr 3-py:dam9dy- o)odes down a rough $37^{\circ}$ inclined plane where the coefficient of kinetic friction is 0.11. 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 log weighing 50lp09y5ksx ymi. 6v+ 5ue/jrh:l n s9gc0 N along a rough surface. The cable attached to the log makes an angle oncrxk g yvlsu0 9py 9:/5ijmh es56.l+f $30.0^{\circ}$ 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 released from rest on a rough inclined plane tilted at an angl.ldn292e xq-9co amzbe oxa -bqdl 99 .2moenzc2f $33.5^{\circ}$ 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 an inclined plane. /h.qiver4qc- y ) hhj3 The angle of incline is gradually increased until the object bveqq)3y rh-4hjh./ icegins to slide. The angle at which this occurs is q. What is the coefficient of static friction between the object and the plane?