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# Recitation class

## 1.

Recitation Class## 2.

Chapter 2## 3.

[Problem 29] A car moving at a constant velocity of 46 m/spasses a traffic cop who is readily sitting on his motorcycle.

After a reaction time of 1.0s, the cop begins to chase the

speeding car with a constant acceleration of 4.0 m/s^2.

How much time does the cop need to overtake the

speeding car?

## 4.

[Problem 29] A car moving at a constant velocity of 46 m/s passes a traffic cop who isreadily sitting on his motorcycle. After a reaction time of 1.0s, the cop begins to chase the

speeding car with a constant acceleration of 4.0 m/s^2. How much time does the cop need

to overtake the speeding car?

Car

Car

Car

## 5.

[Problem 58] An object falls a distance h from rest. If ittravels 0.60h in the last 1.00 s, find (a) the time and (b)

the height of its fall. (c) Explain the physically

unacceptable solution of the quadratic equation in t that

you obtain.?

## 6.

[Problem 58] An object falls a distance h from rest. If ittravels 0.60h in the last 1.00 s, find (a) the time and (b)

the height of its fall. (c) Explain the physically

unacceptable solution of the quadratic equation in t that

you obtain.?

## 7.

[Problem 58] An object falls a distance h from rest. If it travels 0.60h in the last 1.00 s, find(a) the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

+ direction

## 8.

[Problem 58] An object falls a distance h from rest. If it travels 0.60h in the last 1.00 s, find(a) the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

+ direction

## 9.

[Problem 58] An object falls a distance h from rest. If it travels 0.60h in the last 1.00 s, find(a) the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

+ direction

1.00 s

## 10.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 11.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 12.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 13.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 14.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 15.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 16.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

## 17.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

We take

Why?

## 18.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

We take

Why?

Negative time indicates a time before the object was dropped

Answer of (c)

## 19.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

(a) the time of the object’s fall:

Plugging Eq. (3) into (1),

## 20.

[Problem 58] An object falls a distance from rest. If it travels 0.60 in the last 1.00 s, find (a)the time and (b) the height of its fall. (c) Explain the physically unacceptable solution of

the quadratic equation in t that you obtain.?

it travels 0.60 in the last 1.00 s

: time of the object’s fall

+ direction

: one second prior to

1.00 s

(b) the height of the object’s fall:

## 21.

Chapter 4## 22.

[Problem 23] A shell, which is initially located at a distance of abovea horizontal plane, is fired horizontally with a muzzle velocity of to

strike a target on the horizontal plane. (a) How long does the

projectile remain in the air? (b) At what horizontal distance from the

firing point does the shell strike the plane? What are the

magnitudes of the (c) horizontal and (d) vertical components of its

velocity as it strikes the ground?

## 23.

[Problem 23] A shell, which is initially located at a distance of above a horizontal plane, isfired horizontally with a muzzle velocity of to strike a target on the horizontal plane. (a)

How long does the projectile remain in the air? (b) At what horizontal distance from the

firing point does the shell strike the plane? What are the magnitudes of the (c) horizontal

and (d) vertical components of its velocity as it strikes the ground?

t=0

a=-g

## 24.

Chapter 5## 25.

[Problem 49] In the figure, a block of mass kg is pulled along ahorizontal frictionless floor by a cord that exerts a force of

magnitude N at an angle . (a) What is the magnitude of the block's

acceleration? (b) The force magnitude is slowly increased. What is

its value just before the block is lifted (completely) off the floor? (b)

What is the magnitude of the block's acceleration just before it is

lifted (completely) off the floor?

## 26.

[Problem 49] In the figure, a block of mass is pulled along a horizontal frictionless floor bya cord that exerts a force of magnitude at an angle . (a) What is the magnitude of the

block's acceleration? (b) The force magnitude is slowly increased. What is its value just

before the block is lifted (completely) off the floor? (b) What is the magnitude of the

block's acceleration just before it is lifted (completely) off the floor?

(a)

(c) acceleration is

still in the x axis

(b)

before the block is lifted off the floor

## 27.

[Problem 67] The figure shows three blocks attached by cords thatloop over frictionless pulleys. Block B lies on a frictionless table; the

masses are mA = 6.00 kg, mB = 8.00 kg, and mC = 10.0 kg. When the

blocks are released, what is the tension in the cord at the right?

## 28.

[Problem 67] The figure shows three blocks attached by cords that loop over frictionlesspulleys. Block B lies on a frictionless table; the masses are mA = 6.00 kg, mB = 8.00 kg,

and mC = 10.0 kg. When the blocks are released, what is the tension in the cord at the

right?

Assume a clockwise motion

(Downward is positive for block C,

Rightward is positive for block B,

Upward is positive for block A.)

TC

mAg

mCg

## 29.

[Problem 67] The figure shows three blocks attached by cords that loop over frictionlesspulleys. Block B lies on a frictionless table; the masses are mA = 6.00 kg, mB = 8.00 kg,

and mC = 10.0 kg. When the blocks are released, what is the tension in the cord at the

right?

Assume a clockwise motion

(Downward is positive for block C,

Rightward is positive for block B,

Upward is positive for block A.)

TC

mAg

mCg

## 30.

[Problem 67] The figure shows three blocks attached by cords that loop over frictionlesspulleys. Block B lies on a frictionless table; the masses are mA = 6.00 kg, mB = 8.00 kg,

and mC = 10.0 kg. When the blocks are released, what is the tension in the cord at the

right?

Assume a clockwise motion

(Downward is positive for block C,

Rightward is positive for block B,

Upward is positive for block A.)

TC

mAg

mCg

The force for just on block C:

## 31.

Chapter 6## 32.

[Problem 10] In the figure, a block of weight W experiences twoapplied forces, each of magnitude W/2. What coefficient for static

friction between the block and the floor puts the block on the verge

of sliding?

W/2

W/2

30

## 33.

[Problem 10] In the figure, a block of weight W experiences two applied forces, each ofmagnitude W/2. What coefficient for static friction between the block and the floor puts

the block on the verge of sliding?

W/2

W/4

W

W/2

30

## 34.

[Problem 10] In the figure, a block of weight W experiences two applied forces, each ofmagnitude W/2. What coefficient for static friction between the block and the floor puts

the block on the verge of sliding?

W/2

W/4

W

W/2

30

## 35.

[Problem 34] In the figure, a slab of mass rests on a frictionless floor,and a block of mass rests on top of the slab. Between block and

slab, the coefficient of static friction is 0.60, and the coefficient of

kinetic friction is 0.40. A horizontal force of magnitude 100 N begins

to pull directly on the block, as shown. In unit-vector notation, what

are the resulting accelerations of (a) the block and (b) the slab?

## 36.

[Problem 34] In the figure, a slab of mass rests on a frictionless floor, and a block of massrests on top of the slab. Between block and slab, the coefficient of static friction is 0.60,

and the coefficient of kinetic friction is 0.40. A horizontal force of magnitude 100 N begins

to pull directly on the block, as shown. In unit-vector notation, what are the resulting

accelerations of (a) the block and (b) the slab?

Question:

## 37.

[Problem 34] In the figure, a slab of mass rests on a frictionless floor, and a block of massrests on top of the slab. Between block and slab, the coefficient of static friction is 0.60,

and the coefficient of kinetic friction is 0.40. A horizontal force of magnitude 100 N begins

to pull directly on the block, as shown. In unit-vector notation, what are the resulting

accelerations of (a) the block and (b) the slab?

Question:

Block does not stick together !!

80 N

59 N

## 38.

[Problem 34] In the figure, a slab of mass rests on a frictionless floor, and a block of massrests on top of the slab. Between block and slab, the coefficient of static friction is 0.60,

and the coefficient of kinetic friction is 0.40. A horizontal force of magnitude 100 N begins

to pull directly on the block, as shown. In unit-vector notation, what are the resulting

accelerations of (a) the block and (b) the slab?

(a) accelerations of the block

(b) accelerations of the slab

## 39.

[Problem 52] An amusement park ride consists of a car moving in avertical circle on the end of a rigid boom of negligible mass. The

combined weight of the car and riders is 6.0 kN, and the circles'

radius is 10 m. At the top of the circle, what are the (a) magnitude

and (b) direction (up or down) of the force on the car from the

boom if the car’s speed is ? What are (c) and (d) the direction if

## 40.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

car+riders

boom

car and riders

car is at rest at the top

is upward

## 41.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

## 42.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

## 43.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

## 44.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

## 45.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

## 46.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

can be upward

top:

bottom:

## 47.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

car and riders

direction of is able to be upward or downward

(cf. loop-the-loop)

Assuming that is upward, by Newton’s second law

## 48.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

car and riders

m

(a), (b)

the direction of the force from the boom is upward

## 49.

[Problem 52] An amusement park ride consists of a car moving in a vertical circle on theend of a rigid boom of negligible mass. The combined weight of the car and riders is 6.0 kN,

and the circles' radius is 10 m. At the top of the circle, what are the (a) magnitude and (b)

direction (up or down) of the force on the car from the boom if the car’s speed is ? What

are (c) and (d) the direction if

car and riders

m

(c), (d)

the direction of the force from the boom is downward