The force that keeps you from sliding ogqgscs ( no/zb. 7c :1a*xeq+7n cke4hn an icy sidewalk is

  It's more difficult to start moving a heavy carton froqns 1px,a 3 1ggj6uqa9x2j;rcv6 *qv om rest than it is to keep pushing it with constant qa oq239u*x pj1g,1xnrvq66;gva jcsvelocity, because

  A horizontal force accelerates a box from rest acrosp ht;hbwvse-v u.;v 11s a horizontal surface (friction is present) at a constant rate. The experiment is repeated, and allh-se;bp. ;v1thv vuw1 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 inclined ramp atktnc onj4u/3:( 5fjxw8x s lm. constant velocity. Thus we can deduce tha j3mcx 8(s.jtx4nf5wnol u:k/ t

  A block of mass M slides down a frictionless plane inclined at an angle q v8i8xrhw(zh(ke ww .0v.b k gm8q 72jx 6mkfv.with the horizontal. The nor jm 6gmf2i0h7exwvvv 8k 8bk x(8 w.w.qzrk.(hmal reaction force exerted by the plane on the block is

  A block of mass M slides down a frictionless plane i,m c/m;qo*ldt3smz6r nclined at an angle q with the horizontal. The normasmdz6*m qr t,/mo;l c3l reaction force exerted by the plane on the block is directed

  A block of mass M slides down a frictionless plane inclined at fhnbd w*t)f:q3 6bgb6,if-fy an angle q with the horizontaly6b-i f: * t36fbwdqn), fgfbh. The gravitational force is directed

  Two toy cars (28 kg and 3.4 kg) are released .yxs) ic j0k5xa1m e-msimultaneously on an inclined plane that makes an angle of1mmske jx)y0.xa 5c i- $30^{\circ}$ with the horizontal. Make a statement which best describes their acceleration after being released.

  A person of weight 582 N stands omzx b+:t08ky kn a scale in an elevator. What will the scale be reading when the elevator is accele0x +tm:b zkk8yrating downward at $7 \; m/s^2$?

  A person on a scale rides in an elevator. If the mass of the persmd4x0iemw-g9 za2oq 2 on is 60.0 kg and the elevat092qedz- ioa mx2 g4wmor accelerates downward with an acceleration of $4.90 \; m/s^2$, what is the reading on the scale?

  A person on a scale rides in an elevator. If the mass of the persojwlodr 4,0h8g3h fik ,n is 56.2 kg and the elevator accelerates upward with an accele,,wd0 lfr3 j 4hkog8hiration of $11.1 \; m/s^2$, what is the reading on the scale?

  In the Atwood machine shown in Fig. below, if M = 1.75 kg;n. gufp+dt.z q le.m sik3d03 and m = 0.53 kg, what is the magnitude of the acceleratiudmpl .t q0g33.kze.+; ns idfon of the system? (Ignore friction and the mass of the pulley.)

  In the Atwood machine shown in Fg9gs:2a4i1p w faod9tig. below, if M = 0.60 kg and m = 0.40 kg, what is the tension in the string? (Ignore fri:2fgs9 gpiaatw 9 od41ction and the mass of the pulley.)

  A student pulls a box of bookjq(bc et 9wt(j, lcrbr.u-l);s on a smooth horizontal floor 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 50 kg, what is the acceleration of the box?

  A student pulls a box of books on a1 e/bvyjpumx+14v z kdr;w) k* smooth horizontal floor with a force of 100 Nv/)e ypu1rw*m+vkk4jx z d1b ; in a direction 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 b+gfx9. cvq j0in Fig. below. What are the tensicfv .90g jx+qbons in the ropes?

  In Fig. below, if the tensions in the ropes ay:ac ixwq, 5 dzu:bsr-;1ahu 1re 44 $N$, what is the mass of the traffic light?

  Two boxes of masses m and 2m arymk-mc n-s8 f/e in contact with each other on a frictionless surface. (See Fig. below) What is the acc--f smncmk y8/eleration of the more massive box?

  Two boxes of masses m and 2m are in contphqo oq-:6(7xm wnv5q act with each other on a frictionless surface. (See Fig. oox q-(p:q 65w7qnmv hbelow) What is the net force on the more massive box?

  Two boxes of masses m and vvrvgo 91 a0,:rj*zbi 2m are connected by a rope. (See Fig. below) If the forward fov0i,zv:o*j1 vgb 9 rrarce on the more massive box is F, what is the tension in the connecting rope?

  Two boxes of masses m and 2m are connected by a rope. (See Fig. below) fsqk /m8z zwq fnq7 a*86:/, cyq5irrvIf the forward force on the more massive box is F, what is the acceleration of : *yf/q n,qa6kqzrr mf/vw88czs75iqthe less massive box?

  Two boxes are connec)ka*nsq ((cb sted by a cord running over a pulley as shown in Fig. below Box I of mass 9.2 kg rest on the top of the table; the coefficient of kinetic s ba(qcn(s k)*friction between box I and the table is 0.10. Box II has a mass of 13.7 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 frictionsktt76w-+wpj m between a 3.0-kg box and a desk are 7-w6wkpm j +tt0.40 and 0.30, 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 kineticb74r azucs t+n,j5f*b frictions for plastic on wood are 0.43 andbzbas 7 +rj4, ut5cfn* 0.33,
respectively. How much horizontal force would you need to apply to a 4.4 N plastic calculator to start it moving from rest?

  An object slides on a leveh2 z-q*pq,d djl surface in the +x direction. It slows and comes to a stop with d*qpjh2 qd,-za constant acceleration of -$1.66 \; m/s^2$. What is the coefficient of kinetic friction between the object and the floor?

  A 10-kg box sitting on a horizontal su8u;bu y th(:;sq2xg3as b m5sgrface is pulled by a 5.9 $N$ force. A 1.9 $N$ friction force retards the motion. What is the acceleration of the object?

  A horizontal force od+ .hkn o/0qjovy+mlc /cz5 +rf 5.0 N 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 puck is given an initial speed opcc77jt xw6p +f 10 m/s. It slides 50 m on the ice before it stops. What is the coefficit+cc 76jwpxp7ent of kinetic friction between the puck and the ice?

  During the investigation of a traffic ac:zwsm ;o*)4oy0e o ivv2sx,x kcident, police find skid marks 90.0 m long. They determine the coefficient of friction between the car's tires and the rov *om:,vxwey4;oo)s s 0xikz2adway 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 are sta9+ wtkv9ibbk3w1x 4jrcked. (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 boj b3wxr4ktb +19v iwk9x does not slide on the more massive box, what is the static friction force on the less massive box?

  Two boxes of masses m and 3myb .-sictna :) 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 t: b-say)in. cthe more massive box, what is the coefficient of static friction between the boxes?

  An object is on a frictionless inclined plane. The plane is inclined at mrw93i gb+3 iczl8t*zan angle of8rigwlz*t39ib cmz+3 $44^{\circ}$ with the horizontal. What is the object's acceleration?

  A 10-kg mass slides down a flat hill that7mx6v66s;cia0s2wn k l e:cfu 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 inclinev q-r2z1hy1k cqs1x db-n1+fpd 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 inclinedx9wc;n: p uro1fz-s0 z plane tilted 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 down an inclined plane, at a constant velo6r6tsb -rk 8k73kd lvrcity of 3.2 mv8kklrrs3b-r6 tk76d/s.
What is the coefficient of kinetic friction, if the plane makes an angle of $49^{\circ}$ with the horizontal?

  An object with a mass m slides down a r5yigp;l jyd zu-:k0errm2f36ough $37^{\circ}$ 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 dow;yr*e xtp 1e 7yavo hq534-plqn 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 log weighing 500 N along a rough suh mu3r)0q0 uc- ej6 lbz:yx7warface. The cable attached to the log makes an angle of mw:j37l -rx6 uey)ubc 0aq0 hz$30.0^{\circ}$ 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 a- omwm /bx/r2 wd.l9h +ehe;mjt an angle of /ohb- +m;ee2xw./jmrmh w9dl$33.5^{\circ}$ 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. The angle of incline is graduallyy)eml)9oqix 0qi+ g k8 increaseo kxi8q+m e)9lgq iy0)d until the object begins to slide. The angle at which this occurs is q. What is the coefficient of static friction between the object and the plane?