Welty Semester 1 Study guide

A 1kg object has 2.0J of kinetic energy, and hits a wall to come back at half speed. What's its kinetic energy?

.5 J

A stone initially moving at 8.0 m/s on a level surface comes to rest due to friction after it travels 11m. What is the coefficient of kinetic friction between the stone and the surface?

0.3

A 50 kg block is being pulled up a 16 degree slope by a force of 250 N that is parallel to the slope. The coefficient of kinetic friction between the block and the slope is .200. What is the acceleration of the block?

0.412 m/s

In the figure, block A has a mass of 3.00 kg. It rests on a smooth horizontal table and is connected by a very light horizontal string over an ideal pulley to block B, which has a mass of 2.00 kg. When block B is gently released from rest, how long does it take block B to travel 80.0 cm?

0.639

The sum of two vectors of fixed magnitudes has its greatest magnitude when the angle between these two vectors is

0°

A ball is thrown with an initial velocity of 20 m/s at an angle of 60 degrees above the horizontal. If we neglect air resistance, what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

10 m/s

The x component of vector A is 8.7 units, and its y component is -6.5 units. The magnitude of A is closest to

11 units

A car increases its forward velocity uniformly from 40 m/s to 80 m/s while traveling a distance of 200 m. What is its acceleration during this time?

12 m/s

A 10 kg dog is running with a speed of 5.0 m/s. What is the minimum work required to stop the dog in 2.40 seconds?

125 J

The figure shows a 100-kg block being released from the rest from a height of 1.0m. It then takes .53s for it to reach the floor. What is the mass m of the block on the left? There is no friction or mass in the pulley, and the connecting rope is very light.

16 kg

The sum of two vectors of fixed magnitudes has its minimum magnitude when the angle between these two vectors is

180°

An ideal spring stretches by 21.0 cm when a 135-N object is hung from it. If instead you hang a fish from this spring, what is the weight of a fish that would stretch the spring by 31.0 cm?

199 n

The figure shows an object's acceleration-versus-force graph. What is the mass of this object?

2.5 g

A 3.0 kg and a 5.0 kg box rest side by side on a perfectly smooth, level floor. A horizontal force of 32 N is applied to the 3.0 box pushing it against the 5.0 kg box, and, as a result, both boxes slide along the floor. How hard do the two boxes push against each other?

20 N

Vector A has a magnitude of 6.0 m and points 30 degrees north of east. Vector B has a magnitude of 4.0 m and points 30 degrees west of south. The resultant vector A + B is given by

3.2 m at an angle of 8.3º south of east

How much work must be done by a frictional forces in slowing a 1000 kg car from 26.1 m/s to rest?

3.41x10^5

A bead is moving with a speed of 20 m/s at position A on the track shown in the figure. This track is a friction-free, and there is no appreciable air resistance. What is the speed of the bead at point C?

34 m/s

The x component of vector A is 5.3 units, and it's y component is -2.3 unit's. The angle it makes with the x axis is closest to

340°

A ball rolls over the edge of a platform with only a horizontal velocity. The height of the platform is 1.6m and the horizontal range of the ball from the base is 20 m. What is the horizontal velocity of the ball just before it touches the ground?

35 m/s

A sand mover, at a quarry lifts 2,000 kg of sand per minute a vertical distance of 12 m. The sand is initially at rest and is discharged at the top of the sand mover with speed 5.0 m/s into a loading chute. What minimum power must be supplied to this machine?

4.9 kW

A jet plane is launched from a catapult on an aircraft carrier. In 2.0 seconds, it reaches a speed of 42 m/s at the end of the catapult. Assuming the acceleration is constant, how far did it travel during those 2.0 s?

42

Two vectors, of magnitudes 20mm and 50 mm, are added together. Which one of the following is a possible value for the magnitude of the resultant?

44 mm

A car travels at 15 m/s for 10 seconds. It then speeds up with a constant acceleration of 2.0 m/s for 15 seconds. At the end of this time, what is its velocity?

45 m/s

A 10kg mass, hung by an ideal spring, causes the spring to stretch 2.0 cm. What is the spring constant (force constant) for this spring?

49 N/cm

A runner runs around a track with two parallel lines 96m long at the ends of two semi-circles with a radius of 49m. She completed the lap in 100 seconds. What was her average speed?

5 m/s

Vector M = 4.00 m points eastward and vector N = 3.00 m points southward. The resultant vector M + N is given by

5.00 m at an angle of 36.9 degrees south of east

A piano mover raises a 1000 N piano at a constant speed using a very light rope in a frictionless pulley system, as shown in the figure. With what force is the mover pulling down on the rope?

500 N

Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000 kg object moving at 20m/s

500 kg object

Matthew pulls his little sister Sarah along the horizontal ground in a wagon. He exerts a force on the wagon of 60.0 N at an angle of 37.0° above the horizontal. If he pulls her a distance of 12.0 m, how much work does Matthew do?

575 J

A spring loaded dart gun is used to shoot a dart straight up into the air, and the dart reaches a maximum height of 24 meters. The same dart is shot up a second time from the same gun, but this time the spring is compressed only half as far (compared to the first shot). How far does the dart go this time (neglect all friction and assume the spring is ideal)?

6 m

Three vectors, S, T, and U, have the components shown in the table. What angle does the resultant of these three vectors make with an +x axis? PART 2: What is the magnitude? X- component y- component S -3.5m 4.5m T 0.00m -6.5m U 5.5m -2.5m

66 degrees below x axis ; 2.00m

Three vectors, S, T, U have components in table, what angle results of these vectors with the x axis?

66° below the x axis (add up the tables)

A car accelerates from 5.0 m/s to 2 m/s at a constant rate of 3.0 m/s^2. How far does it travel while accelerating?

69 m

What is the mass of an object that experiences a gravitational force of 685 N near Earth's Surface when g = 9.80 m/s^2?

69.9 kg

A car of mass 1100 kg that is traveling at 27 m/s starts to slow down and comes to a complete stop in 578 m. What is the magnitude of the average braking force acting on the car?

690 N

If a vector A has components Ax = -3.0 lb and Ay = -4.0 lb, and vector B has components Bx = 3.0 lb and By = -8.0 lb, what is the magnitude of vector C=A-B?

7.2 lb

At what minimum rate is a 60.0-kg boy using energy when in 8.00 s, he runs up a flight of stairs that is 10.0-m high?

735 W

The components of vectors B and C are given as follows: Bx=-9.2 Cx=-4.5 By=-6.1 Cy=4.3 The angle (less than 180 degrees) between vectors B and C is closest to

77°

As shown in the figure, a 10 kg block on a perfectly smooth horizontal table is connected by a horizontal string to a 63 kg block that is hanging over the edge of the table. What is the magnitude of the acceleration of the 10 kg block when the other block is gently released?

8.5 m/s

Vector A has a magnitude of 6.0 m and points 30° north of east. Vector B has a magnitude of 4.0 m and points 30° east of north. The resultant vector A+B is given by

9.7 m at an angle of 42° north of east

If vector A has components Ax<0 and Ay>0, then the angle that this vector makes with the positive x-axis must be in the range

90° to 180°

An ideal spring with a spring constant (force constant) of 22 N/m is stretched from equilibrium to 2.9 m. How much work is done in the process?

93 J

How much work would a child do while pulling a 12-kg wagon a distance of 4.3m with a 22N force?

95 J

An object is moving with a constant positive acceleration. The acceleration versus time graph of this object is

A horizontal straight line

An object is moving with a constant positive acceleration. The POSITION versus TIME graph of this object is

A parabolic curve

An object is moving with a constant positive acceleration. The VELOCITY versus TIME graph of this object is

A straight line making an angle with the time axis

An object is moving with constant non-zero velocity in the +x-direction. The position vs time graph of this object is

A straight line making an angle with the time axis

The graph shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched. For which one of the graphs does the spring obey Hooke's law?

B

Person X pushes twice as hard against a stationary brick wall as person Y. Which one of the following statements is correct?

Both do zero work

Consider two vectors A and B shown in the figure. The difference A-B is best illustrated by

C

A bucket is being lowered with a constant downward velocity, the tension in the rope must be

Equal to the weight of the bucket

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about Normal Force F on the block due to the ramp?

F = mg cosθ

A fireman slides down a fire pole and accelerates. What happens when his hands equal the force of his weight?

He descends but slows and slows

Two boxes P and Q are on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force F is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

Less than F, but not zero

Vector A has a magnitude of 6.0 m and points 30º east of south. Vector B has a magnitude of 4.0 and points 30º west of north.The resultant vector A+B is given by

Magnitude 2, with 60º south of east

Consider a car that travels between points A and B. The car's average speed can be greater than the magnitude of its average velocity, but the magnitude of its average velocity can never be greater than its average speed.

True

The slope of a velocity versus time graph gives

acceleration

A 75-N box rests on a perfectly smooth horizontal surface. The minimum force need to start the box moving is

any horizontal force greater than zero

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about force of static friction f on the block?

f=mg sin θ

Which of the following graphs represent an object having zero acceleration?

graphs A and B

An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be

greater than the weight of the elevator

When a ball is thrown straight up with no air resistance, the acceleration at its highest point

is downward

An object is moving with constant non-zero velocity. Which of the following statements about it must be true?

the net force on the object is zero

Swimmers at a water park have a choice of two frictionless waterslides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2?

v1=v2

The slope of a position versus time graph gives

velocity

When is the average velocity of an object equal to the instantaneous velocity?

when the velocity is constant

The magnitude of A is 5.5m, and this vector lies in the second quadrant and makes an angle of 34° with the y-axis. The components of A are closest to:

x -3.1m, y +4.6m

A 1.0 kg object moving in a certain direction has a kinetic energy of 2.0 J. It hits a wall and comes back with half its original speed. What is the kinetic energy of this object at this point?

.5 J

A cart starts from rest and accelerates uniformly at 4.0 m/s^2 for 5.0s. It next maintains the velocity it has reached for 10s. Then it slows down at a steady rate of 2.0 m/s for 4 seconds. What is the final speed of the car

12 m/s

A 10-kg dog is running with a speed of 5m/s. What is the work required to stop the dog in 2.4s?

125 J

The components of vectors A and B are given as follows: Ax = 7.6 Bx = -5.1 Ay = -9.2 BY = -6.8 What is the magnitude of the vector difference B - A?

13

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is .30. A horizontal 140N force is applied to the box. What is the friction force on the box?

140 N

A girl throws a rock horizontally, with a velocity of 10 m/s from a bridge. It falls 20 meters to the water below. How far does the rock travel horizontally before striking the water, without air resistance?

20 m

A car starts from rest and accelerates at a steady 6.00 m/s. How far does it travel in the first 3.00 seconds?

27.0 m/s

If a vector A has components Ax > 0, and Ay < 0, then the angle that this vector makes with the positive x-axis must be in the range

270° to 360°

The figure shows a block of mass M hanging at rest. The light wire fastened to the wall is horizontal and has a tension of 38 N. The wire fastened to the ceiling is also very light, has a tension of 99 N, and makes an angle 0 with the ceiling. Find the angle 0.

50°

If I weight 741 N on Earth at a place where g=9.8 m/s and 5320 N on the surface of another planet, what is the acceleration due to gravity on that planet?

70.4 m/s

Two displacement vectors have magnitudes of 5.0 m and 7.0m, respectively. If these two vectors are added together, the magnitude of the sum

Could be as small as 2.0 m or as large as 12 m

In the figure, what does the spring scale read? The pulleys are ideal and the strings and scale are also massless.

Exactly 1.0 N

An object is moving with constant non-zero velocity in the +x direction. The VELOCITY versus TIME graph of this object is

Horizontal straight line

An object moving in the +x direction experiences an acceleration of +2.0 m/s. This means the object

Is increasing its velocity by 2.0 m/s every second

Two objects of unequal masses, M and m (M > m) are connected by a very light cord passing over an ideal pulley of negligible mass. When released, the system accelerates, adn friction is negligible. Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?

M has more gravity than m

Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5 min longer. Compare the work they do on the car.

Neither of them do work

A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory

Neither the ball's velocity nor its acceleration are zero

A crate is sliding down an inclined ramp at a constant speed of .55 m/s. The vector sum of all the forces acting on this crate must be point

None of the above choices is correct

You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that the train is

Slowing down

Two boxes are connected to each other by a string as shown in the figure. The 10N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension T in the string?

T < 30 N

A ball is thrown downward in the absence of air resistance. After it has been released, which statement concerning its acceleration is correct?

The acceleration is constant

Suppose that a car traveling to the west begins to slow down as it approaches a traffic light. Which of the following statements about its acceleration is correct?

The acceleration is toward the east.

Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by this object

The displacement is either less than or equal to the distance traveled

A fireman is sliding down a fire pole. As he speeds up, he tightens his grip on the pole, thus increasing the vertical frictional force that the pole exerts on the fireman. When the force on his hands equals his weight, what happens to the fireman?

The fireman continues to descend, but with constant speed.

Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which one of the following statements about these objects is correct?

The two objects reach the bottom of the ramp at exactly the same time

Three cars (F, G, H) are moving with the same speed and slam on their breaks. The most massive car is car F, and the least massive car is car H. If the tires of all three cars have identical coefficients of kinetic friction with the road surface, which car travels the longest distance to skid to a stop?

They all travel the same distance in stopping

Consider that a deer runs from point A to point B. The distance the deer runs can be greater than the magnitude of its displacement, but the magnitude of displacement can never be greater than the distance it runs.

True

An object is moving with constant non-zero velocity in the +x direction. The POSITION versus TIME graph of this object is

a straight line making an angle with the time axis