Question 1

A 1000-kg car is moving at 15 km/h.If a 2000-kg truck has 23 times the kinetic energy of the car,how fast is the truck moving?

Accepted Answer

Kinetic energy is proportional to mass and the square of velocity. So, if the truck has 23 times the kinetic energy of the car, then its velocity must be sqrt(23) times that of the car. The car is moving at 15 km/h, so the truck must be moving at sqrt(23) * 15 = 51 km/h.

Question 2

It requires 0.30 kJ of work to fully drive a stake into the ground.If the average resistive force on the stake by the ground is 
How long is the stake?

Accepted Answer

The answer of It requires 0.30 kJ of work to...

Question 3

How much kinetic energy does a 0.30-kg stone have if it is thrown at

Accepted Answer

The formula for kinetic energy is K.E. = 1/2 mv^2, where m is the mass and v is the velocity (speed). 
Here, the mass of the stone is 0.30 kg and the velocity is 11 m/s. 
Plugging these values into the formula, we get: 
K.E. = 1/2 x 0.30 kg x (11 m/s)^2 = 290.25 J (rounded to two decimal places). 
Therefore, the best choice is A) 290 J.

Question 4

A 30-N box is pulled upward 6.0 m along the surface of a ramp that rises at 37° above the horizontal.How much work does gravity do on the box during this process?

Accepted Answer

Gravity does no work on the box because the force of gravity is perpendicular to the displacement of the box. The work done on the box is equal to the work done by the person pulling the box up the ramp against gravity. The calculation for this work is:

Work = force x distance x cos(theta)

where force is the component of the force vector that is parallel to the displacement, distance is the distance over which the force is applied, and theta is the angle between the force vector and the displacement.

In this case, the force is equal to the weight of the box (30 N) times the sin of the angle of the ramp (37°) because this is the component of the weight that is parallel to the ramp. The distance is equal to the length of the ramp (6.0 m), and cos(theta) is equal to the cosine of the angle of the ramp (37°). Plugging in these values, we get:

Work = (30 N) x (sin 37°) x (6.0 m) x (cos 37°) ≈ 110 J

Therefore, the correct answer is B.

Question 5

You carry a 7.0-kg bag of groceries 
Above the ground at constant speed across a 
Room.How much work do you do on the bag in the process?

Accepted Answer

When you carry the bag of groceries at a constant speed, you are not changing its kinetic energy. Therefore, the work done on the bag is zero, since work is the change in energy. So, the only possible answer is A) 0.00 J.

Question 6

A person carries a 25.0-N rock through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 1.50 min.How much work did gravity do on the rock between A and B?

Accepted Answer

Gravity does not do any work on the rock as it is carried horizontally from point A to point B. Work is only done if there is a force applied in the direction of the displacement. In this case, the force of gravity acting on the rock is perpendicular to the displacement from A to B, so no work is done.

Question 7

A crane lifts a 425 kg steel beam vertically upward a distance of How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s²? Neglect frictional forces.

Accepted Answer

The answer of A crane lifts a 425 kg steel...

Question 8

How much work would a child do while pulling a 12-kg wagon a distance of 
With a 
Force?

Accepted Answer

The answer of How much work would a child do...

Question 9

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 s?

Accepted Answer

The answer of A 10-kg dog is running with a...

Question 10

What is the minimum energy needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

Accepted Answer

The minimum energy needed can be calculated using the kinetic energy formula: $ \Delta KE = \frac{1}{2} m (v_f^2 - v_i^2) $, where $ m = 1600 \, \text{kg} $, $ v_f = 40.0 \, \text{m/s} $, and $ v_i = 15.0 \, \text{m/s} $. Plugging in the values, $ \Delta KE = \frac{1}{2} \times 1600 \times (40^2 - 15^2) = 1.10 \times 10^6 \, \text{J} = 1.10 \, \text{MJ} $.

Question 11

When a car of mass Accelerates from 10.0 m/s to some final speed,4.00 × 10⁵ J of work are done.Find this final speed.

Accepted Answer

The answer of When a car of mass 
Accelerates from...

Question 12

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?

Accepted Answer

The kinetic energy of an object is given by the equation KE = (1/2)mv^2, where m is the mass of the object and v is its speed. Initially, the object has a kinetic energy of 2.0 J. When it hits the wall and comes back with half its original speed, its new speed is (1/2)v. Using the equation for kinetic energy, we can find the new kinetic energy:

KE' = (1/2)m(1/2v)^2 = (1/8)mv^2 = (1/8)(2.0 J) = 0.25 J

Therefore, the kinetic energy of the object at this point is 0.50 J, or choice C.

Question 13

A person carries a 2.00-N pebble through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 6.75 min.How much work did gravity do on the rock between A and B?

Accepted Answer

The work done by gravity is given by the formula W = mgh, where m is the mass of the object, g is the acceleration due to gravity, and h is the change in height. Since the pebble ends at the same height as it started (same horizontal line), there is no change in height and therefore no work done by gravity. The answer must be negative since the pebble is moving upwards against the force of gravity, so the only possible answer is B.

Question 14

Find the net work done by friction on a box that moves in a complete circle of radius 
On a uniform horizontal floor.The coefficient of kinetic friction between the floor and the box is 0.25,and the box weighs

Accepted Answer

The answer of Find the net work done by friction...

Question 15

A traveler pulls on a suitcase strap at an angle 36° above the horizontal.If 
Of work are done by the strap while moving the suitcase a horizontal distance of 
What is the tension in the strap?

Accepted Answer

The answer of A traveler pulls on a suitcase strap...

Question 16

How much work must be done by frictional forces in slowing a 1000-kg car from 
To rest?

Accepted Answer

The answer of How much work must be done by...

Question 17

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?

Accepted Answer

The work done by Matthew can be calculated using the formula:

work = force x distance x cos(theta)

where force is 60 N, distance is 12 m, and theta is the angle between the force and the direction of motion (37 degrees in this case).

Plugging in the values, we get:

work = 60 N x 12 m x cos(37 degrees)
     = 575 J

Therefore, the answer is C, 575 J.

Question 18

A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope.The tree house is 
Above the ground.What is the mass of the box?

Accepted Answer

The answer of A child does 350 J of work...

Question 19

An object hits a wall and bounces back with half of its original speed.What is the ratio of the final kinetic energy to the initial kinetic energy of the object?

Accepted Answer

The final kinetic energy of the object is proportional to the square of its velocity, so if the object bounces back with half of its original speed, its final kinetic energy will be $(1/2)^2 = 1/4$ of its original kinetic energy. Therefore, the ratio of the final kinetic energy to the initial kinetic energy is 1/4, which corresponds to choice B.

Question 20

A stone with a mass of 1.0 kg is tied to the end of a light string which keeps it moving in a circle with a constant speed of 4.0 m/s on a perfectly smooth horizontal tabletop.The radius of the path is 0.60 m.How much work does the tension in the string do on the stone as it makes one-half of a complete circle?

Accepted Answer

The tension in the string is always perpendicular to the displacement of the stone, so the work done by tension is zero. The only force doing work is gravity, but it is also perpendicular to the displacement of the stone, so it does no work either. Therefore, the total work done on the stone is zero.

Quiz 7: Work and Kinetic Energy

A 1000-kg car is moving at 15 km/h.If a 2000-kg truck has 23 times the kinetic energy of the car,how fast is the truck moving?

It requires 0.30 kJ of work to fully drive a stake into the ground.If the average resistive force on the stake by the ground is How long is the stake?

How much kinetic energy does a 0.30-kg stone have if it is thrown at

A 30-N box is pulled upward 6.0 m along the surface of a ramp that rises at 37° above the horizontal.How much work does gravity do on the box during this process?

You carry a 7.0-kg bag of groceries Above the ground at constant speed across a Room.How much work do you do on the bag in the process?

A person carries a 25.0-N rock through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 1.50 min.How much work did gravity do on the rock between A and B?

A crane lifts a 425 kg steel beam vertically upward a distance of How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s2? Neglect frictional forces.

How much work would a child do while pulling a 12-kg wagon a distance of With a Force?

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 s?

What is the minimum energy needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

When a car of mass Accelerates from 10.0 m/s to some final speed,4.00 × 105 J of work are done.Find this final speed.

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?

A person carries a 2.00-N pebble through the path shown in the figure,starting at point A and ending at point B.The total time from A to B is 6.75 min.How much work did gravity do on the rock between A and B?

Find the net work done by friction on a box that moves in a complete circle of radius On a uniform horizontal floor.The coefficient of kinetic friction between the floor and the box is 0.25,and the box weighs

A traveler pulls on a suitcase strap at an angle 36° above the horizontal.If Of work are done by the strap while moving the suitcase a horizontal distance of What is the tension in the strap?

How much work must be done by frictional forces in slowing a 1000-kg car from To rest?

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?

A child does 350 J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope.The tree house is Above the ground.What is the mass of the box?

An object hits a wall and bounces back with half of its original speed.What is the ratio of the final kinetic energy to the initial kinetic energy of the object?

A crane lifts a 425 kg steel beam vertically upward a distance of How much work does the crane do on the beam if the beam accelerates upward at 1.8 m/s²? Neglect frictional forces.

When a car of mass Accelerates from 10.0 m/s to some final speed,4.00 × 10⁵ J of work are done.Find this final speed.