Question 1

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.How much work is done by the campers in pulling the equipment 1000 m if its speed is increasing at the constant rate of 0.20 m/s²?

Accepted Answer

The work done by the campers is equal to the change in kinetic energy of the system.

We can find the initial kinetic energy of the system using:

KE = (1/2)mv^2

where m is the mass of the equipment and v is its initial velocity (which we know is 0 since it is being pulled from rest).

m = 6000 N / 9.81 m/s^2 = 611.8 kg

KE = (1/2)(611.8 kg)(0 m/s)^2 = 0 J

The final kinetic energy of the system can be found using:

KE = (1/2)mv^2

where v is the final velocity of the equipment.

v = at

where a is the acceleration of the equipment and t is the time it takes to travel 1000 m.

a = Fnet/m = (Fpull - Ffriction)/m = [(6000 N)(0.05) - 0]/611.8 kg = 4.91 m/s^2

t = 2d/v = 2(1000 m) / (0 m/s + 0.20 m/s^2)t = 10000 s

v = (0 m/s) + (0.20 m/s^2)(10000 s) = 2000 m/s

KE = (1/2)(611.8 kg)(2000 m/s)^2 = 2.447 x 10^9 J

The work done by the campers is then:

W = KEfinal - KEinitial = 2.447 x 10^9 J - 0 J = 2.447 x 10^9 J

W ≈ 4.2 x 10^15 J ≈ 4.2 x 10^15/10^15 = 4.2 x 10^0 = 4.2 J

Therefore, the best choice is D, 4.2 x 10^15 J.

Question 2

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m.An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around.The work done by the external force as the mass makes one revolution is:

Accepted Answer

C

Question 3

The weight of an object on the moon is one-sixth of its weight on the Earth.The ratio of the kinetic energy of a body on the Earth moving with speed V to that of the same body moving with speed V on the moon is:

Accepted Answer

The kinetic energy of a body is given by the formula $KE = \frac{1}{2}mv^2$, where $m$ is the mass of the body and $v$ is its velocity. This formula shows that kinetic energy is independent of the location of the body (whether on Earth or the moon) as it only depends on the mass and velocity of the body. Since the mass and velocity of the body remain the same in both locations, the ratio of the kinetic energies is 1:1.

Question 4

An object moves in a circle at constant speed.The work done by the centripetal force is zero because:

Accepted Answer

The work done by a force is zero if the force is perpendicular to the direction of displacement. In circular motion, the centripetal force always acts perpendicular to the velocity of the object, hence no work is done by the centripetal force.

Question 5

An object of mass 1 kg is whirled in a horizontal circle of radius 0.5 m at a constant speed of 2 m/s.The work done on the object during one revolution is:

Accepted Answer

The work done on an object is given by the formula:
Work = force x distance x cos(theta)
In this case, the force acting on the object is towards the center of the circle and is given by the formula:
Force = (mass x velocity^2) / radius

Plugging in the given values, we get:
Force = (1 kg x 2 m/s^2) / 0.5 m = 4 N

Since the force is perpendicular to the displacement of the object (which is along the circle), the angle theta between force and displacement is 90 degrees. Therefore, cos(theta) = 0.

Thus, the work done on the object is:
Work = 4 N x 2piR x 0 = 0 J

Therefore, the best choice is A) 0 J.

Question 6

A crate is initially at rest on a horizontal frictionless table.A constant horizontal force F is applied.Which of the following five graphs is a correct plot of work W as a function of crate speed v?

Accepted Answer

The answer of A crate is initially at rest on...

Question 7

Two trailers, X with mass 500 kg and Y with mass 2000 kg, are being pulled at the same speed.The ratio of the kinetic energy of Y to that of X is:

Accepted Answer

Kinetic energy is directly proportional to the mass of the object and to the square of its velocity. Since the two trailers are being pulled at the same speed, the ratio of their kinetic energies is simply the ratio of their masses:

$KE_Y/KE_X = m_Y/m_X = 2000/500 = 4/1$

Therefore, the ratio of the kinetic energy of Y to that of X is 4:1.

Question 8

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.The work done by the campers in pulling the equipment 1000 m at constant velocity is:

Accepted Answer

The work done is calculated using the formula: Work = Force x Distance. The force of friction is the product of the coefficient of kinetic friction and the normal force (which is equal to the weight of the equipment, 6000 N). Thus, the force of friction is 0.05 x 6000 N = 300 N. The work done over 1000 m is 300 N x 1000 m = 3.0 x 10^5 J.

Question 9

A man pulls a sled along a rough horizontal surface by applying a constant force  at an angle $\theta$above the horizontal.In pulling the sled a horizontal distance d, the work done by the man is:

Accepted Answer

The work done by the man can be calculated using the formula W = Fd cosθ, where W is the work done, F is the applied force, d is the horizontal distance traveled, and θ is the angle between the applied force and the horizontal. Therefore, the correct answer is B, as it corresponds to this formula.

Question 10

Which of the following is NOT a correct unit for work?

Accepted Answer

Work is defined as the product of force and displacement in the direction of the force, and its SI unit is the joule. Erg, joule, and newton-meter are all correct units for work, reflecting different systems of measurement (CGS, SI, and the metric system, respectively). The option with "watt" is incorrect because a watt is a unit of power, not work. Power is the rate at which work is done or energy is transferred.

Question 11

Which of the following bodies has the largest kinetic energy?

Accepted Answer

Kinetic energy is given by the formula $KE = \frac{1}{2}mv^2$. For each option: A) $KE = \frac{1}{2} \cdot 3M \cdot V^2 = \frac{3}{2}MV^2$, B) $KE = \frac{1}{2} \cdot 3M \cdot (2V)^2 = 6MV^2$, C) $KE = \frac{1}{2} \cdot 2M \cdot (3V)^2 = 9MV^2$, D) $KE = \frac{1}{2} \cdot M \cdot (4V)^2 = 8MV^2$. Thus, the body with mass $2M$ and speed $3V$ has the largest kinetic energy.

Question 12

A boy holds a 40-N weight at arm's length for 10 s.His arm is 1.5 m above the ground.The work done by the force of the boy on the weight while he is holding it is:

Accepted Answer

The work done by the force of the boy on the weight is zero since the weight is not displaced in any direction. Work is defined as a force applied over a displacement. In this case, the weight is held stationary at arm's length, so there is no displacement and therefore no work done.

Question 13

A 2-kg object is moving at 3 m/s.A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m.The work done by this force is:

Accepted Answer

The work done by a force is calculated using the formula Work = Force x Distance. Here, the force is 4 N and the distance over which it is applied is 5 m. Therefore, the work done is 4 N * 5 m = 20 J.

Question 14

An 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied.The car skids to a stop in 4.0 s.How much kinetic energy does the car lose in this time?

Accepted Answer

The answer of An 8000-N car is traveling at 12...

Question 15

An object is constrained by a cord to move in a circular path of radius 0.5m on a horizontal frictionless surface.The cord will break if its tension exceeds 16N.The maximum kinetic energy the object can have is:

Accepted Answer

The maximum kinetic energy (KE) is related to the tension in the cord and the radius of the circular path. The tension (T) provides the centripetal force necessary for circular motion, which can be expressed as $T = \frac{mv^2}{r}$, where $m$ is the mass of the object, $v$ is its velocity, and $r$ is the radius of the circular path. The kinetic energy is given by $KE = \frac{1}{2}mv^2$. Substituting the expression for tension into the kinetic energy formula gives $KE = \frac{T \cdot r}{2}$. Given that $T = 16N$ and $r = 0.5m$, the maximum kinetic energy is $KE = \frac{16N \cdot 0.5m}{2} = 4J$.

Question 16

A particle moves 5 m in the positive x direction while being acted upon by a constant force  = (4 N)  + (2 N  )- (4 N)  .The work done on the particle by this force is:

Accepted Answer

The answer of A particle moves 5 m in the...

Question 17

Which of the following groups does NOT contain a scalar quantity?

Accepted Answer

Both displacement and acceleration are vector quantities, meaning they have both magnitude and direction. Force, another option in this group, can be either a vector or a scalar quantity depending on the context.

Question 18

A crate moves 10 m to the right on a horizontal surface as a woman pulls on it with a 10-N force.Rank the situations shown below according to the work done by her force, least to greatest.

Accepted Answer

The answer of A crate moves 10 m to the...

Question 19

Which of the following is the correct combination of dimensions for energy?

Accepted Answer

The dimension of energy is derived from the formula for kinetic energy or potential energy, which is mass (M) times length squared (L^2) divided by time squared (T^2), giving the dimension ML^2/T^2.

Question 20

A sledge (including load)weighs 5000 N.It is pulled on level snow by a dog team exerting a horizontal force on it.The coefficient of kinetic friction between sledge and snow is 0.05.How much work is done by the dog team pulling the sledge 1000 m at constant speed?

Accepted Answer

The answer of A sledge (including load)weighs 5000 N.It is...

Quiz 7: Kinetic Energy and Work

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.How much work is done by the campers in pulling the equipment 1000 m if its speed is increasing at the constant rate of 0.20 m/s²?

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m.An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around.The work done by the external force as the mass makes one revolution is:

The weight of an object on the moon is one-sixth of its weight on the Earth.The ratio of the kinetic energy of a body on the Earth moving with speed V to that of the same body moving with speed V on the moon is:

An object moves in a circle at constant speed.The work done by the centripetal force is zero because:

An object of mass 1 kg is whirled in a horizontal circle of radius 0.5 m at a constant speed of 2 m/s.The work done on the object during one revolution is:

A crate is initially at rest on a horizontal frictionless table.A constant horizontal force F is applied.Which of the following five graphs is a correct plot of work W as a function of crate speed v?

Two trailers, X with mass 500 kg and Y with mass 2000 kg, are being pulled at the same speed.The ratio of the kinetic energy of Y to that of X is:

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.The work done by the campers in pulling the equipment 1000 m at constant velocity is:

Which of the following is NOT a correct unit for work?

Which of the following bodies has the largest kinetic energy?

A boy holds a 40-N weight at arm's length for 10 s.His arm is 1.5 m above the ground.The work done by the force of the boy on the weight while he is holding it is:

A 2-kg object is moving at 3 m/s.A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m.The work done by this force is:

An 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied.The car skids to a stop in 4.0 s.How much kinetic energy does the car lose in this time?

An object is constrained by a cord to move in a circular path of radius 0.5m on a horizontal frictionless surface.The cord will break if its tension exceeds 16N.The maximum kinetic energy the object can have is:

A particle moves 5 m in the positive x direction while being acted upon by a constant force = (4 N) + (2 N ) - (4 N) .The work done on the particle by this force is:

Which of the following groups does NOT contain a scalar quantity?

A crate moves 10 m to the right on a horizontal surface as a woman pulls on it with a 10-N force.Rank the situations shown below according to the work done by her force, least to greatest.

Which of the following is the correct combination of dimensions for energy?

A sledge (including load) weighs 5000 N.It is pulled on level snow by a dog team exerting a horizontal force on it.The coefficient of kinetic friction between sledge and snow is 0.05.How much work is done by the dog team pulling the sledge 1000 m at constant speed?

Quiz 7: Kinetic Energy and Work

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.How much work is done by the campers in pulling the equipment 1000 m if its speed is increasing at the constant rate of 0.20 m/s2?

A 0.50-kg object moves in a horizontal circular track with a radius of 2.5 m.An external force of 3.0 N, always tangent to the track, causes the object to speed up as it goes around.The work done by the external force as the mass makes one revolution is:

The weight of an object on the moon is one-sixth of its weight on the Earth.The ratio of the kinetic energy of a body on the Earth moving with speed V to that of the same body moving with speed V on the moon is:

An object moves in a circle at constant speed.The work done by the centripetal force is zero because:

An object of mass 1 kg is whirled in a horizontal circle of radius 0.5 m at a constant speed of 2 m/s.The work done on the object during one revolution is:

A crate is initially at rest on a horizontal frictionless table.A constant horizontal force F is applied.Which of the following five graphs is a correct plot of work W as a function of crate speed v?

Two trailers, X with mass 500 kg and Y with mass 2000 kg, are being pulled at the same speed.The ratio of the kinetic energy of Y to that of X is:

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.The work done by the campers in pulling the equipment 1000 m at constant velocity is:

A man pulls a sled along a rough horizontal surface by applying a constant force at an angle θ\thetaθ above the horizontal.In pulling the sled a horizontal distance d, the work done by the man is:

Which of the following is NOT a correct unit for work?

Which of the following bodies has the largest kinetic energy?

A boy holds a 40-N weight at arm's length for 10 s.His arm is 1.5 m above the ground.The work done by the force of the boy on the weight while he is holding it is:

A 2-kg object is moving at 3 m/s.A 4-N force is applied in the direction of motion and then removed after the object has traveled an additional 5 m.The work done by this force is:

An 8000-N car is traveling at 12 m/s along a horizontal road when the brakes are applied.The car skids to a stop in 4.0 s.How much kinetic energy does the car lose in this time?

An object is constrained by a cord to move in a circular path of radius 0.5m on a horizontal frictionless surface.The cord will break if its tension exceeds 16N.The maximum kinetic energy the object can have is:

A particle moves 5 m in the positive x direction while being acted upon by a constant force = (4 N) + (2 N ) - (4 N) .The work done on the particle by this force is:

Which of the following groups does NOT contain a scalar quantity?

A crate moves 10 m to the right on a horizontal surface as a woman pulls on it with a 10-N force.Rank the situations shown below according to the work done by her force, least to greatest.

Which of the following is the correct combination of dimensions for energy?

A sledge (including load) weighs 5000 N.It is pulled on level snow by a dog team exerting a horizontal force on it.The coefficient of kinetic friction between sledge and snow is 0.05.How much work is done by the dog team pulling the sledge 1000 m at constant speed?

Camping equipment weighing 6000 N is pulled across a frozen lake by means of a horizontal rope.The coefficient of kinetic friction is 0.05.How much work is done by the campers in pulling the equipment 1000 m if its speed is increasing at the constant rate of 0.20 m/s²?