Friction Questions and Answers

2 In the given figures find the accelerations and the friction forces involved u 0 5kg A U 0 5 5kg A F 15N i p 0 5 10kg B ii u 0 5 10kg B u 0 5 5kg A iii p 0 5 10kg B G G 200N u 0 5 5kg A iv u 0 5 10kg B 30N G 90N G

46 A uniform chain is placed at rest on a rough surface of base length and height h on an irregular surface as shown in Fig 7 294 Then the mini mum coefficient of friction between the chain and the surface must be equal to a C h 21 3h b 11 h 1 2h h Fig 7 29

2 A conveyor belt is moving at a constant speed of 2 m s A box is gently dropped on it The coefficient of friction between them is 0 5 The distance that the box will move relative to belt before coming to rest on it taking g 10 ms 2 is AIPMT Mains 2011 2 0 4 m 4 06 m 1 Zero 2 12 m

block of mass 100 kg lying steady on the horizontal surface of a table needs 20 N horizontal force to come into motion What is the coefficient of static friction between the block and the surface of table A 0 2 C 0 5 B 0 02 D 0 05

One end of a uniform ladder rests against a smooth ver tical wall and the other end is on rough ground A man of 80 kg weight stands on the ladder at th up its length Angle of the ladder with the horizontal is 30 Find the reaction of the wall and the coefficient of fric tion between the ladder and the ground The mass of the ladder is 40 kg 678 96 N 12

3 A block of mass m 10 kg rests on a horizontal table The coefficient of friction between the block and the table is 0 05 When hit by a bullet of mass 50 g moving with speed v that gets embedded in it the block moves and comes to stop after moving a distance of 2 m on the table If a freely falling object were to acquire V speed after being dropped from height 10 H then neglecting energy losses and taking g 10 ms 2 the value of H is close to 1 0 2 km 2 0 3 km 3 0 4 km 4 05 1

Which of the following equations represents the motion of a body moving with constant finite acceleration in these equations y denote the displacement in time t and p q and r are arbitary constants 1 y p qt 2 r pt 2 p tar 31 p t q t r 1 4 y p qt r y independen of time

Q Example 6 A block of mass 1 kg is pushed against a rough vertical wall with a force of 20 N coefficient of static friction being 1 Another horizontal force of 10 N ts applied on the block in a direction parallel to the wall Will the block move If yes in which direction If no find the frictional force exerted by the wall on the block g 10 m s 4 Solution Normal reaction on the block from the wall will be N F 20 N Therefore limiting friction Weight of the block is fi UN l a 20 5 N W mg 1 10 10 N A horizontal force of 10 N is applied to the block The resultant of these two forces will be 10 2 N in the direction shown in figure Since this resultant is greater than the limiting friction The block will move in the direction of Fnet with acceleration Fnet fL 10 2 5 m 1 9 14 m s F 20 N 10 N Fig 5 125 Fnet 10v2 N A 45 Fig 5 126 10 N

A circular disc with a groove along its diameter is placed horizontally A block of mass 1 kg is placed as shown The co efficient of friction between the block and all a 25 m s surfaces of groove in contact is 2 5 The disc has an acceleration of 25 m s Find the acceleration of the block with respect to disc 9 cos 0 4 5 sin 0 3 5 2011 2006

A small cube mass m is on the inner curved surface of a funnel rotating about its own axis Its wall inclines at an angle with the horizontal The cube is kept at a distance r from the vertical axis of rotation of the funnel If the coefficient of friction between the funnel and the cube is for what frequency of rotation of the funnel will the cube remain at rest on the surface of the funnel It is implied that the cube will roll down if the funnel remains stationary on un Caterw 1 g sino Fucose

A body of mass 10 kg is about to slide down a plane inclined at an angle 20 with the horizontal What force along the plane if applied upwards will just make the body slide upwards sin 20 0 3420 67 032 N

38 A block is placed on a rough plane whose inclination to the horizontal 0 can be varied The angle of repose is 30 The graph that correctly indicates the variation of the frictional force f between the block and the plane with 0 is 4 L 30 1 3 0 0 2 4 30 30 0 0

What is the maximum value of force so that both the blocks will move together H 0 64 2 kg F 3 kg P 0 2 Tum

3 3 22 A rough vertical board has a horizontal acc Lion a so that a 2kg block pressing against it does not fall The coefficient of friction between the block and the board should be 2 a 86 0 1 greater than or equal to 2 kg 3 less than or equal to 26 g a

A truck of mass 1000 kg pulls a trailer of mass 3000 kg using a rope Frictional force between truck and road and trailer and road are 1000 N and 2000 N respectively If the truck engine applies a force of 8000 N i what is the acceleration of the trailer and ii what is the ten sion in the rope between the truck and the trailer Ans i 1 25 m s 2 ii 5750 N

0 Starting from rest a body slides down a 45 inclined plane in twice the time it takes to slide down the same distance in the absence of friction The coefficient of friction between the body and the inclined plane is 1988 a 0 80 c 0 25 b 0 75 d 0 33

Find the minimum force that must be applied on the block vertically so that the block does not move a 70 N 10 kg 100 N 0 5 b 80 N c 50 N d 100 N

placed on a horizontal conveyor belt which is moving with uniform velocity v as shown in the figure The coefficient of static friction is t the coefficient of kinetic friction is H and the acceleration of gravity is g Initially the object slips for a while but finally moves without slipping together with the belt Q20 How far the conveyor belt moves while the object is slipping B A g 2 g 4 8 D 24 8

Which of these is an example of sliding friction O A a flying kite pushed by a gentle breeze OB a badminton shuttlecock flying over the net OC a basketball rolling across a wooden floor D a hockey puck moving across the ice

A block weighing 300 N is moved at a constant speed over a of 50 N applied parallel to the surface What does the constant speed tell you about the ces acting on the block a raw a force diagram for the block b C d What is the mass of the block 0 591 981 Find the Normal Force F of the block My C S 201 Calculate the coefficient of kinetic friction uk ND 9 77 7

Suppose a 1 0 N force is applied to the side of a 4 0 kg block that is sitting on a table The block experiences a frictional force against the force that is applied a Draw a force diagram for the block b C What is the weight of the block F e What is the normal force on the block FN d If the coefficient of kinetic friction is 20 what is the frictional force on the block F 6 80 FEMIN 15 j What is the net force on the block to N a ecf ol Is What is the acceleration of the block from the net force

The first step in determining fault at the crash scene is to determine the coefficient of friction between the tires and the road Here is what you know 1 A team was sent to the scene to complete the data collection needed for you to determine the coefficient of friction To do this the data collecto drags a 13 265kg tire across the pavement The force meter shows a force of 100N is needed to drag the car tire at constant velocity We also knc that the coefficient of friction for the truck s tires is only 70 of the value for the car s tires Calculate the coefficient of friction for the truck tires There are points assigned for your work as well as the answer

What is the mass percent of oxygen 16 00 g mol in NaHCO 84 07 g mol 57 10 a b 22 21 c 67 56 d 0 20 ANS a What is the mas percent of oxygen 16 00 g mol in Ca3 PO4 2 310 18 g mol a 23 6 b 41 2 c 30 1 d 58 4 ANS b Compositional Stoichiometry and Mass Percentage Using Actual Masses What is the mass percent of oxygen in 0 35 g NaHCO3 a 57 10 b 22 21 c 67 56 d 0 20 ANS a What is the mas percent of oxygen in 1 55 g of Ca3 PO4 2 a 23 6 b 41 3 c 30 1 d 58 4

What are the two types of friction Give an example If forces are acting in the same direction what would we do to get the net force If forces are acting in opposite directions what would we do to get the net force

In which of the scenarios are the objects interacting through a force of fluid friction Scenario 1 A bottle filled with soda rolls across the surface of a concrete patio Scenario 2 Scenario 3 Scenario 4 A sugar glider launches itself and glides from branch to branch A car parked on a steep icy driveway slides downhill A water boarder skis across the surface of a lake O A Scenarios 1 and 3 OB Scenarios 1 and 4 OC Scenarios 2 and 3 O D Scenarios 2 and 4

9 A bullet is moving at a speed of 367 m s when it embeds into a lump of moist clay The bullet penetrates for a distance of 0 0621 m Determine the acceleration of the bullet while moving into the clay T

2 Determine the coefficient of friction between the Prius tires and the ice Explain how you did this and show all your work 1 Because this car is equipped with anti lock brakes the wheels alternate between locked and rolling We can use the car s motion to determine the effective or average coefficient of friction during this motion Hint Can you tell from the video exactly when the driver begins to brake

An incline plane has 40 0 and 0 15 Starting from rest how long will it take a 4 0 kg block to reach a speed of 12 m s EN

horizontal A force of friction of 60 0 N impedes the motion of the box a What is the force pulling the box down the incline 7 b What is the acceleration of the box down the incline 135 67 12 1 60 Za 1 2 22 taut F75 67 c How long will it take the box to reach the bottom of the incline SO 8 15 67 12a az 57 72 124 4 8104 10 75 67 2 60 195 15 47 conts 2 775 38 d What is the coefficient of kinetic friction between the box and the surface of the incline

Problem 3 Block A with mass 2 kg is placed on top of Block B with mass 5 kg The coefficient of kinetic friction between B and the ground is 0 2 A horizontal force F is applied to B a Draw a free body diagram for each block What force accelerates A b If both blocks accelerate to the right at 3 m s what is the magnitude of F c Find the minimum coefficient of static friction between the blocks such that both blocks can accelerate at 3 m s without A slipping

1 Two blocks are connected by a massless string over a frictionless pulley as shown in the diagram K UOBJ 2 3 0 80 kg PK 0 14 60 Pk 0 14 2 0 kg a Determine the acceleration of the blocks b Calculate the tension in the string c If the string broke for what minimum value of the coefficient of static friction would the 2 0 kg block not begin to slide

0 8c6p26 In the figure a sled being held on an inclined plane by a cord pulling directly up the plane The sled is to be on the verge of moving up the plane In the lower figure data blotted with the magnitude F required of the cord s force on the sled is plotted versus a range of values for the coeffient of static friction us between sled and plane F 1 50 N F 3 75 N and H 0 560 At what angle 9 is the plane inclined deg Fo F F Ho Hs

8c6p85 A car weighing 1 07x10 N and traveling at 14 20 m s attempts to round an unbanked curve with a radius of 60 m What force of friction is required to keep the car on Circular path Submit Answer Tries 0 8 If the coefficient of static friction between the tires and road is 0 500 is the attempt at taking the curve successful

5 3 00 m A B 6 00 m C www A 10 0 kg block is released from point A The track is frictionless except for the portion between B and C which has a length of 6 00 m The block travels down the track hits a spring of force constant k 2250 N m and compresses the spring 0 300m from its equilibrium position before coming to rest momentarily a Calculate the energy lost due to friction b Determine the coefficient of friction between B and C

A 30 0 kg block is being pushed up a 15 0 slope by a force of 250 0 N which is parallel to the slope What is the coefficient of kinetic friction between the block and the slope if the block is moving up the slope at a constant velocity Push

A 50 kg block rests on a horizontal surface The coefficient of static friction us 0 50 The coefficient of kinetic friction uk 0 3 A force of 200 N is applied as shown T The block accelerates to the right The block remains at rest The block does not move until the force is increased to greater than 490 N The block moves and chtinues to move at constant velocity No conclusions can be drawn concerning the movement of the block from the information given

When a horizontal force of 190 N is applied to a 69 kg box on a leveled floor the box slides with constant velocity What is the magnitude of the friction force in N on the box Your Answer

A block of unknown mass sits at rest on a surface where the coefficient of static friction is 0 8 You apply a horizontal force to the block and find that it requires a force of 200 N to start the motion of the block If you move the block to a location where the coefficient of static friction is 0 4 what horizontal force do you need to apply to get the box to move 400 N 50 N 200 N 800 N 100 N

A 5 kg box is on a rough horizontal surface An external force F is applied horizontally to the box When force F equals 4 N the box is in motion at constar velocity When force F equals 5 N the acceleration of the box is closest to 0 m s 0 2 m s 0 5 m s 1 m s

A person is moving a sofa across the floor at a constant speed applying a constant horizontal force After this the person doubles the magnitude of the force How does the motion of the sofa change after the force was increased It moves at a greater constant speed first it moves with an increasing speed and then continues with a greater constant speed with a continuously increasing speed first it moves at a constant speed and then with an increasing speed

No picture no points 3 10 pts A 20 kg crate is being pulled horizontally at a constant rightward velocity of 2 0 m s along a rough floor The pulling force of 36 N makes an angle of 30 degrees to the horizontal Find the coefficient of friction between the crate and the floor

Response A dog sled driver prepared for her race Her sled was loaded with equipment but on snow and ice the dogs moved the heavy sled Each dog pulled with a force of 600 N During the race she came to an area of grass and dirt instead of snow The sled slowed to a stop The driver said There must be something wrong with one of the dogs One of them is pulling with a force of less than 600 N How would you respond to the dog sled driver

block of mass m 1 5 kg is kept in place on a rough ramp by a spring as shown The ramp makes an angle 50 wrt to orizontal and the coefficients of static and kinetic frictions are 0 65 and 0 3 respectively The spring constant is k 40N m k Axmin www m Hw Hs What is Ain the minimum amount the spring must be stretched in order for the block to be at rest D a Ax 0 043 m b Ax 0 053 m Dor 0 13 m

3 A skater moves across the ice a distance of 12 m before a constant frictional force of 15 N causes him to stop His initial speed is 2 2 m s Calculate the skater s mass 74 kg 4 Could an elephant walking slowly across a field have more kinetic energy than a cheetah chasing its prey Explain your answer yes

You are moving into a new place, and you rented a U-Haul cargo van to transport your home furniture and different boxes. Moving the boxes from the house to the van is done through a dolly you are using. However, the dolly has broken during a move. There are still several boxes which must now be carried manually from the home to the van. The ramp leading into the mover's van is at a 30° angle to the ground. You are carrying a box weighing 200 N from the house. You are placing the box on the ramp, planning to push it the rest of the way into the van 1) Create a formula relating the frictional force, the weight of the box, the force applied and the angle of inclination of the ramp, given the net force parallel to the ramp is zero. 2) The mover fastens a rope to the box, and pulls, applying a force of 200 N at an angle of 15° to the ramp. The box still does not move. Determine the new frictional force. 3) Adjust your formula from question 2, to include the angle between the ramp and the applied pulling force, given the net force parallel to the ramp is zero.

A student pulls a sled carrying a box with a force of 51 N. The sled weighs 12 kg and has a coefficient of friction of 0.36 with the ground. What is the acceleration of the sled? Assume the coefficient of static friction and kinetic friction are the same. 0.54 m/s² 0.82 m/s² 0.65 m/s² 0.72 m/s²

Exploration 1.1 Have one of the group press horizontally against a stool using only the index finger. No one should be sitting on the stool. The person pushing the stool should begin by pushing lightly against the stool and increase the force of the push until the stool moves. cevitos)do Describe the static friction. Was it constant until the stool moved or did it change? Explain your reasoning in the space below, osht strenqrooni bedt megelb ybed sont wesh ot olds od o'r

A 5.3 kg block rests on a level surface. The coefficient of static friction is μ = 0.67, and the coefficient of kinetic friction is μ* = 0.48 A horizontal force, F, is applied to the block. As F is increased, the block begins moving. Describe how the force of friction changes as F increases from the moment the block is at rest to when it begins moving. Show how you determined the force of friction at each of these times - before the block starts moving, at the point it starts moving, and after it is moving. Show your work.

An object moving on a frictionless horizontal road with a constant speed of 40 m/s decreases to 15 m/s 5 s after entering a road where the friction force is constant. If the mass of the object is 4 kg, what is the friction force acting on the object, in N'? A) 10 B) 15 C) 20 D) 25 E) 30

Mr. Mangan pulls a 90 kg block with a force of 250 N at an angle of 15 degrees. The coefficient of kinetic friction between the block and the floor is 0.25. Draw the Free Body Diagram, find the net force, and find the acceleration of the block.