exam question guide

In the picture below, a girl is sitting motionless on a swing. What isthe net force on the girl?

0 newtons exam 6

A block is pushed across a horizontal surface by the force F with constantvelocity. F = 20 N,𝜃 = 30°, and M = 10 kg. What is the magnitude of the normalforce on t he block?

108 N exam 6

The position of an object is given by x = at3 - bt2 + ct. The instantaneous acceleration ofthe object at time t is

6at-26 exam 6

What is the smallest value of the force F such that the 2.0-kg block will notslide down the wall? The coefficient of static friction between the block and the wallis 0.2.

98 N

13)Terminal velocity can be described as...

A)the maximum speed an object can travel falling towards earth. exam 7

Which of the following would increase the sliding friction betweenyour foot and the floor?

A. Increasing the weight on your foot.

How can the force of friction between two surfaces be reduced?

By separating surfaces with a lubricant.

Which of the following statements about friction is TRUE?

Friction is a force that resists motion.

A toy rocket engine is securely fastened to a large puck that can glide with negligible friction over a horizontal surface, taken as the xy plane. The 4.80-kg puck has a velocity of 2.00î m/s at one instant. Eight seconds later, its velocity is (6.00î + 4.0ĵ) m/s. (a) Assuming the rocket engine exerts a constant horizontal force, find the components of the force. (b) Find its magnitude.

HW 5 Q2

Two forces act on a 4.40 kg object, the gravitational force and a second, constant force. The object starts from rest and in 1.20 s is displaced (4.60î − 3.30ĵ) m. Write the second force in unit vector notation. (Enter your answer in kg · m/s2. Assume the gravitational force acts in the −ĵ direction.)

HW 5 Q3

Two forces 1 and 2 act on a 7.20-kg object. F1 = 30.0 N and F2 = 13.0 N. Find the acceleration of the object for the configuration of forces shown in Figure (a). magnitude direction

HW5 Q4

A woman has a weight of 201 lb. Calculate the following. (a) her weight in newtons (b) her mass in kilograms

HW5 Q5

A 17.0 lb box is placed on the ground. (a) What force (in lb) does the ground exert on the box? (b)A cord is attached to the box and run through a pulley directly above the box, so that the cord is vertical. The free end of the cord is then connected to a hanging weight. Calculate the force exerted by the ground on the box (in lb), if the hanging weight is 12.0 lb. (c) A 33.5 lb weight is substituted for the 12.0 lb weight. Calculate the new force (in lb) exerted by the floor on the box.

HW5 Q6

The systems shown below are in equilibrium with m = 5.40 kg and 𝜃 = 28.0°. If the spring scales are calibrated in newtons, what do they read? Ignore the masses of the pulleys and strings and assume the pulleys and the incline are frictionless.

HW5 Q7

Assume the three blocks (m1 = 1.0 kg, m2 = 2.0 kg, and m3 = 2.5 kg) portrayed in the figure below move on a frictionless surface and a force F = 48 N acts as shown on the 2.5 kg block (a) Determine the acceleration given this system (in m/s2 to the right). (b) Determine the tension in the cord connecting the 2.5 kg and the 1.0 kg blocks (in N). (c)Determine the force exerted by the 1.0 kg block on the 2.0 kg block (in N). (d)What If? How would your answers to parts (a) and (b) of this problem change if the 2.0 kg block was now stacked on top of the 1.0 kg block? Assume that the 2.0 kgblock sticks to and does not slide on the 1.0 kg block when the system is accelerated. (Enter the acceleration in m/s2 to the right and the tension in N.)

HW5 Q8

A woman at an airport is towing her 18.5 kg suitcase at constant speed by pulling on a strap at an angle 𝜃 above the horizontal (see figure). She pulls on the strap with a 35.7 N force, and the friction force on the suitcase is 20.0 N. (b) What angle does the strap make with the horizontal (in degrees)? (c)What is the magnitude of the normal force that the ground exerts on the suitcase (in N)? (d) What If? If the woman still pulls on the strap with a 35.7 N force but wishes to accelerate the suitcase at a rate of 0.500 m/s2, at what angle (in degrees) must she pull on the strap? Assume that the rolling friction is independent of the angle of the strap.

HW6 Q1

A 2.40-kg block starts from rest at the top of a 30.0° incline and slides a distance of 1.70 m down the incline in 1.00 s. (a) Find the magnitude of the acceleration of the block. (b) Find the coefficient of kinetic friction between block and plane. (c) Find the friction force acting on the block. (d) Find the speed of the block after it has slid 1.70 m.

HW6 Q2

A cord passing over a pulley connects two masses, as shown, where m1 = 3.60 kg and m2 = 6.50 kg. The system accelerates with a magnitude of 1.03 m/s2. The coefficient of kinetic friction between the masses and the incline is the same for both masses. Assume the pulley is frictionless, and the cord is massless. (a) What is the coefficient of kinetic friction? (b) What is the tension (in N) in the cord?

HW6 Q3

Consider a conical pendulum with a bob of mass m = 95.0 kg on a string of length L = 10.0 m that makes an angle of 𝜃 = 3.00° with the vertical. (Consider +î to be towards the center of the circular path and +ĵ to be upward.) (a) Determine the horizontal and vertical components of the force exerted by the string on the pendulum. (b) Determine the radial acceleration of the bob.

HW6 Q4

A car initially traveling eastward turns north by traveling in a circular path at uniform speed as in the figure below. The length of the arc ABC is 221 m, and the car completes the turn in 38.0 s. (a) What is the acceleration when the car is at B located at an angle of 35.0°? Express your answer in terms of the unit vectors î and ĵ. (b) Determine the car's average speed. (c) Determine its average acceleration during the 38.0-s interval.

HW6 Q5

You are riding on a Ferris wheel that is rotating with constant speed. The car in which you are riding always maintains its correct upward orientation; it does not invert. (a) What is the direction of the normal force on you from the seat when you are at the top of the wheel?

HW6 Q6

Charlie is playing with his daughter Torrey in the snow. She sits on a sled and asks him to slide her across a flat, horizontal field. Charlie has a choice of pushing her from behind by applying a force downward on her shoulders at 30° below the horizontal (figure (a)) or attaching a rope to the front of the sled and pulling with a force at 30°above the horizontal (figure (b)). Which would be easier for him?

HW6 Q7

The driver of a speeding truck slams on the brakes and skids to a stop through a distance d. On another trial, the initial speed of the truck is half as large. What now will be the truck's skidding distance?

HW6 Q8

A worker pushes a m = 3.00 kg box a distance d = 7.20 m along the floor by a constant force of magnitude F = 16.0 N directed at an angle 𝜃 = 26.0° below the horizontal as shown in the figure. Assume the floor is frictionless. (Enter your answers in joules.) (a) Determine the work done on the box by the applied force (the force on the box exerted by the worker). (b)Determine the work done on the box by the normal force exerted by the floor. (c) Determine the work done on the box by the gravitational force. (d) Determine the work done by the net force on the box.

HW7 Q1

A shopper in a supermarket pushes a cart with a force of 28.0 N directed at an angle of 25.0° below the horizontal. The force is just sufficient to balance various friction forces, so the cart moves at constant speed. (a) Find the work done by the shopper on the cart as she moves down a 55.1-m-long aisle. (b)The shopper goes down the next aisle, pushing horizontally and maintaining the same speed as before. If the work done by frictional forces doesn't change, would the shopper's applied force be larger, smaller, or the same? (c) What about the work done on the cart by the shopper?

HW7 Q2

The force acting on a particle varies as shown in the figure below. (The x axis in the graph has its tickmarks marked in increments of 2.50 m.) Find the work done by the force on the particle as it moves across the following distances.

HW7 Q3

One end of a light spring with spring constant k1 = 1,300 N/m is attached to the ceiling. A second light spring is attached to the lower end, with spring constant k2 = 1,700 N/m. An object of mass 1.50 kg is attached to the lower end of the second spring. (a) By how much does the pair of springs stretch (in m)?

HW7 Q4

A rock with a mass of 4.00 kg is moving with velocity (6.60î − 2.20ĵ) m/s. (HINT: v2 = v · v.)

HW7 Q5

A woman pushes a 35.0 kg box at a constant speed for 10.6 m along a level floor, doing 410 J of work by applying a constant horizontal force of magnitude F on the box.

HW7 Q6

A 440-N child is in a swing that is attached to a pair of ropes 2.10 m long. Find the gravitational potential energy of the child-Earth system relative to the child's lowest position at the following times. (a) when the ropes are horizontal

HW7 Q7

An object is subjected to a friction force with magnitude 3.09 N, which acts against the object's velocity. What is the work (in J) needed to move the object at constant speed for the following routes?

HW7 Q8

One or more external forces, large enough to be easily measured, are exerted on each object enclosed in a dashed box shown in the figures below. Identify the reaction to each of these forces. (Select all that apply.)

Homework 5 Q1

A 15-kg block sits at rest on a horizontal surface. The coefficients of friction between the block and the surface are μs = 0.50 and μk =0.35. a. the magnitude of the friction force on the block is currently:

Problem 1, practice exam 6 (Free Response)

A box of mass m is pulled with a constant acceleration a along a horizontal frictionlessfloor by a wire that makes an angle of θ above the horizontal. If T is the tension in thiswire, then

T > ma. exam 6 q9

7)An object moves in a circular path at a constant speed. Compare the direction of the object's velocity andacceleration vectors.

The vectors are perpendicular. exam 7

Is it possible for an object moving with a constant speed to accelerate? Explain.

Yes, although the speed is constant, the direction of the velocity can be changing. Exam 7 MC 6

Consider an object moving along a straight line. Which one of these is impossible?

a is zero when v is increasing.

What type of acceleration does an object moving with constant speed in a circular path experience?

centripetal acceleration. exam 7

A 9kg hanging weight is connected by a string over a pulley to

exam 6

A block of mass m = 2.0kg is held in equilibrium on an incline of angle q = 60oby the horizontal force F, as shown in Fig. (a) Determine the value of F,the magnitude of F.

exam 6 FR 3

A block of mass m1 = 3.70 kg on a frictionless inclined plane of angle q = 30.0ois connected by a cord over a massless, frictionless pulley to a second block of massm2 = 2.30 kg hanging vertically, as shown in Fig. What are (a)the magnitude of the acceleration of each block and

exam 6 FR4

Find the tension in each cord for the systems shown in Fig. (Neglect the mass of thecords.)

exam 6 Q4

In a football game, _____'s 250-lb quarterback runs head-on into Nebraska's 320-lbtackle. While our quarterback is plowing over the Nebraska tackle, what is true about themagnitudes of the forces?

exam 6 Q6

Consider a conical pendulum with a bob of massm = 80.0 kg on a string of lengthL = 10.0 m that makes an angle ofθ = 5.00° with the vertical. (Consider +î to be towards the centerof the circular path and +ĵ to be upward.)(a)Determine the horizontal and vertical components of the force exerted by the string onthe pendulum.

exam 7 FR Q1

A 12.0-kg flying pig is suspended by a cable while moving in a horizontal circle of radius r = 94.4 cm at a constant speed of 4.00 m/s. a) How large (in m/s2) is the flying pig's centripetal acceleration?b) How large is the centripetal force on the pig? What force (or force component) provides thepig's centripetal force?

exam 7 FR Q2

A car initially traveling eastward turns north by traveling in a circular path at uniform speed as in the figure below. The length of the arcABC is 235 m, and the car completes the turn in 35.0 s. (a) What is the acceleration when the car is atB located at an angle of 35.0°? Express youranswer in terms of the unit vectorsî andĵ.

exam 7 FRQ3

Base on the information below answer the questions 3-4-5 Harry sets some clay (m = 3.25 kg) on the edge of a pottery wheel (r = 0.600 m), which is initially motionless. He then begins to rotate the wheel with a uniform acceleration, reaching a final angular speed of 2.400 rev/s in 3.00 s, while not touching the clay. As a result, the clay is subject to a tangential and centripetal acceleration while it sits on the edge of the wheel.

exam 7 MC 3,4,5

A racquetball has a radius of 0.0295 m. The drag coefficient of the ball is 0.52, andthe density of the air is 1.29 kg/m3. What would be the terminal speed for theracquetball if it were dropped from a very high cliff, assuming it has a massof 0.0399 kg?

exam 7 MC Q1

Escaping from a tomb raid gone wrong, Lara Croft (m = 59.0 kg) swings across analligator-infested river from a 9.10-m-long vine. If her speed at the bottom of theswing is 5.30 m/s and she makes it safely across the river, what is the minimumbreaking strength of the vine?

exam 7 MC Q2

21)A metal plate which is 3 m long and 0.5 m wide is placed in a stream of fluid flowing at 0.5m/s.The density of the fluid is 800kg/m3 and the drag force is measured and found to be 30 N. Calculatethe drag coefficient.

exam 7, 0.2

19)What is the centripetal acceleration of a skater moving with a tangential speed of 2.0 m/s in acircular path with radius 2.0 m?

exam 7, 2.0 m/s^2

22)Calculate the drag force for a cylindrical disc of 0.4 m radius, in a wind blowing at 30m/s, giventhat the drag coefficient is 0.8. [The density of air is 1.2 kg/m3].

exam 7, 217N

15)What forces are acting on a dropped book that is falling to the floor?

exam 7, Gravity and air resistance

A motorcyclist moves at a constant speed down one hill and up another hill along the smoothcurved surface. When the motorcyclist reaches the lowest point of the curve its velocity andacceleration directions are

exam 7, MC Q17

16)This test paper is sitting at rest on your desk. Which of the following statements best describes thissituation?

exam 7, The forces acting on the paper are balanced.

14)Which object will hit the ground first if dropped at the same time at the same height in a perfectvacuum?

exam 7, They will hit at the same time.

10)When an object experiences uniform circular motion, the direction of the net force is

exam 7, is directed toward the center of the circular path.

20)Centripetal force can be calculated from centripetal acceleration by

exam 7, multiplying by the mass.

18)What is the translational speed of an object in circular motion called?

exam 7, tangential speed

Consider a ball on a fixed-length string being whirled in a vertical circular path as shown in the diagram below.(a)When the ball is at the bottom of the circle, what is the direction of the tension forceon the ball? Use the direction rosette to answer this question.(b)When the ball is at the bottom of the circle, what is the direction of the gravitationalforce on the ball? Use the direction rosette to answer this question.(c)When the ball is at the bottom of the circle, what is the direction of the centripetalforce on the ball? Use the direction rosette to answer this question.(d)When the ball is at the bottom of the circle, what is the expression for the centripetalforce on the ball? Take the upward direction as positive and the downward directionas negative when considering the sign of the forces. (Use the following asnecessary:m, g andT.)(e)If the speed of the ball at the bottom of the circle isv, what is the expression for thecentripetal force on the ball in terms of its speedv and the lengthL of the string?Take the upward direction as positive and the downward direction as negative whenconsidering the sign of the forces. (Use the following as necessary:m, v andL.)

exam 8 FRQ 2

What is the ideal banking angle for a gentle turn of 1.40 km radius on a highway witha 115 km/h speed limit (about 71 mph), assuming everyone travels at the limit?

exam 8 FRQ1

A box of unknown mass is sliding with an initial speed vi = 5.90 m/s across a horizontal frictionless warehouse floor when it encounters a rough section of flooringd = 3.10 m long. The coefficient of kinetic friction between the rough section of flooring and the box is 0.100. Using energy considerations, determine the final speed of the box (in m/s) after sliding across the rough section of flooring.

exam 8 FRQ3

How fast must a 2.7-g ping-pong ball move in order to have the same kinetic energy as a 145 g baseball moving at 34.0 m/s?

exam 8 FRQ4

A store uses an elevator to move items from one level to another. The elevator has a mass of 750 kg and moves upward with constant acceleration for 2.50 s until it reaches its cruising speed of 1.75 m/s. (Note: 1 hp = 746 W.)(a)What is the average power (in hp) of the elevator motor during this time interval? (b)What is the motor power (in hp) when the elevator moves at its cruising speed?

exam 9 FRQ1

In a truck-loading station at a post office, a small 0.200-kg package is released from rest at point A on a track that is one- quarter of a circle with radius 1.60 m. The size of the package is much less than 1.60 m, so the package can be treated as a particle. It slides down the track and reaches point B with a speed of 4.80 m/s. From point B, it slides on a level surface a distance of 3.00 m to point C, where it comes to rest. (a) What is the coefficient of kinetic friction on the horizontal surface?

exam 9 FRQ2

A wooden block with mass1.50 kg is placed against a compressed spring at the bottom of an incline of slope 30.0° (point A). When the spring is released, it projects the block up the incline. At point B, a distance of 6.00 m up the incline from A, the block is moving up the incline at 7.00 m/s and is no longer in contact with the spring. The coefficient of kinetic friction between the block and the incline is 𝜇D= 0.50. The mass of the spring isnegligible. Calculate the amount of potential energy that was initially stored in the spring.

exam 9 FRQ3

A force that resists motion is called:

friction

The acceleration of a block sliding down a frictionless incline with an angle θ abovehorizontal is

gsin(theta)

The tread on the bottom of your sneakers is designed to:

increase the friction between your foot and the ground.

When an object experiences uniform circular motion, the direction of the acceleration is

is directed toward the center of the circular path. exam 7

11)A car goes around a curve of radius r at a constant speed v. Then it goes around the same curve at half of theoriginal speed. What is the centripetal force on the car as it goes around the curve for the second time, compared tothe first time?

one-fourth as big. exam 7

A 3.0kg mass undergoes an acceleration given by a = (2.0i + 5.0j) m/s. Find the resultantforce F and its magnitude.

practice exam 6 Q1

While two forces act on it, a particle of mass m = 3.2kg is to move continuously withvelocity (3 ms )i−(4 ms )j. One of the forces is F1 = (2 N)i+(−6N)j. What is the otherforce?

practice exam 6 Q2

If a man weighs 875N on Earth, what would he weigh on Jupiter, where the free-fallacceleration is 25.9 m/s2 ?

practice exam 6 Q3

A 12.0 kg block is pulled at constant speed on a table surface by a horizontal cord with a tension of 25.0 N. It was noticed that it initially required a tension of 35.0 N just to get the block started moving. a. How large is the normal force of the table acting on the block

practice exam 6 free response Q2

The friction force that resists the motion between two surfaces thatare not moving is called:

static friction

12)Terminal velocity occurs when ___________.

the force of gravity and air resistance are equal. exam 7

A student attempts to slide a block down a smooth,dry ramp as shown, but the block does not move.The most likely explanation is that:

the static friction between the block and the ramp is greater thanthe force of gravity pulling the box down the ramp.

The coefficient of kinetic friction is less than the coefficient of staticfriction.

true

A car is moving down a straight road at constant speed. The net force on the car is equalto

zero