Question 1

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 a force is calculated by multiplying the force by the distance moved in the direction of the force. In this case, the boy is not moving the weight, so the distance moved is zero. Therefore, the work done by the force of the boy on the weight is also zero.

Question 2

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

A

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

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

Accepted Answer

Displacement and acceleration are vector quantities because they have both magnitude and direction. Force is a vector quantity as it has magnitude and direction; energy is a scalar quantity as it has only magnitude. Option C also contains all scalar quantities. Option D has distance, which is a scalar quantity. Option E has weight, which is a vector quantity as it depends on both mass and gravitational acceleration.

Question 5

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 6

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 force they apply multiplied by the distance the equipment is moved. We can find the force applied by using the equation for kinetic friction:

$f_k = \mu_k N$

where $f_k$ is the force of kinetic friction, $\mu_k$ is the coefficient of kinetic friction, and $N$ is the normal force (equal to the weight of the equipment here, which is 6000 N).

$f_k = 0.05 	imes 6000 = 300$ N

The force applied by the campers is equal in magnitude to the force of kinetic friction since the equipment is moving at a constant speed, so the force they apply is also 300 N.

The work done is:

$W = Fd = 300 	imes 1000 = 300000$ J

However, the equipment's speed is increasing, so there must be an additional force applied to it. This force is given by:

$F = ma$

where $m$ is the mass of the equipment (found by dividing its weight by the acceleration due to gravity, which is 9.8 m/s$^2$), and $a$ is the acceleration, which is 0.20 m/s$^2$.

$m = 6000/9.8 = 612.2$ kg

$F = 612.2 	imes 0.20 = 122.4$ N

The total work done by the campers is:

$W = Fd = (300+122.4) 	imes 1000 = 422400$ J

Rounding to one decimal place, we get:
$W = 4.2 	imes 10^5$ J, which corresponds to choice (D).

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 mass and velocity squared. Since the two trailers are being pulled at the same speed, the ratio of their kinetic energy can be found using the ratio of their masses:
KEY/ KEX = (1/2) MY V^2 / (1/2) MX V^2
KEY/KEX = MY/MX
KEY/KEX = 2000/500
KEY/KEX = 4:1

Question 8

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 9

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 answer of Camping equipment weighing 6000 N is pulled...

Question 10

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

The answer of A 0.50-kg object moves in a horizontal...

Question 11

Which of the following bodies has the largest kinetic energy?

Accepted Answer

The kinetic energy of a body is given by the formula KE = (1/2)mv^2. Thus, we can calculate the kinetic energy of each body as follows:
A) KE = (1/2)(3M)V^2 = (3/2)MV^2
B) KE = (1/2)(3M)(2V)^2 = 6MV^2
C) KE = (1/2)(2M)(3V)^2 = 9MV^2
D) KE = (1/2)M(4V)^2 = 8MV^2

Therefore, we can see that body C has the largest kinetic energy with 9MV^2.

Question 12

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 is equal to the force applied multiplied by the distance moved in the direction of the force. In this case, the force is at an angle above the horizontal, so we need to find the component of the force that is in the horizontal direction, which is Fd cosθ.

Question 13

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 14

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 15

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 answer of A 2-kg object is moving at 3...

Question 16

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 the object during one revolution is given by the formula W = F*d*cosθ, where F is the force applied, d is the distance traveled, and θ is the angle between F and d. In this case, the force applied is the tension in the string that keeps the object in circular motion. Since the tension force is perpendicular to the direction of motion, θ = 90 degrees and cosθ = 0. Therefore, the work done is zero, regardless of the distance traveled or the speed of the object.

Question 17

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 18

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 19

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

Accepted Answer

The answer of Which of the following is the correct...

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....

Quiz 7: Kinetic Energy and Work

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 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:

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:

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

Which of the following is NOT a correct unit for 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?

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:

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?

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 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:

Which of the following bodies has the largest kinetic energy?

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:

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.

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 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 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?

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

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

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 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:

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:

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

Which of the following is NOT a correct unit for 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?

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:

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?

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 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:

Which of the following bodies has the largest kinetic energy?

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:

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.

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 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 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?

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

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?

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: