Work, Energy and Simple Machines

Calculate the work done when a force of $10\ N$ displaces a body by $10\ m$ in its own direction.

A boy carries a bucket of water and walks $5\ m$ on a level road. The work done by the boy against gravity is:

The work done on an object does NOT depend upon the:

If a force $F$ acts on an object and the object covers a distance $s$, the expression for work is $W = Fs$. This is true only when:

A man pulls a trolley on a horizontal surface by applying a force at an angle. The work done will be zero if:

If the force is $20\ N$ and the work done is $1\ J$, the displacement in the direction of the force is:

Work done by a person in climbing a ladder depends on:

A weightlifter holds a $100\text{ kg}$ barbell above his head for $10\text{ seconds}$ without moving it. How much scientific work is done on the barbell during these $10\text{ seconds}$?

A car is traveling at a constant speed on a highway. The work done by the engine is used to:

A force $\vec{F}$ is perpendicular to the displacement $\vec{s}$. The scalar product $\vec{F} \cdot \vec{s}$ results in which value of work?

A stretched spring has potential energy. When it is released, this energy converts into:

In most energy transformations, some energy is released as 'waste' heat. Does this violate the law of conservation of energy?

Joule is the unit of:

The total energy of a ball mid-air (ignoring air resistance) is:

An object of mass $m$ is released from rest at a height $H$ above the ground (Position A). At a certain point B during its free fall, its kinetic energy is twice its potential energy ($KE = 2 \times PE$). Assuming no energy is lost to air resistance, what is the height $h$ of the object at point B in terms of $H$?

A weightlifter holds a $100\text{ kg}$ barbell steady above his head for $5$ seconds. While he feels exhausted, the work done on the barbell is zero. What happens to the chemical energy he spends?

An object is dropped from a height of $40\text{ m}$. After it has fallen through a distance of $10\text{ m}$, what is the ratio of its potential energy to its kinetic energy at that point?

If a stone is projected vertically upwards from the ground with a speed $u$, the ratio of its kinetic energy to potential energy at a height $h$ ($h < u^2/2g$) is:

A bullet fires from a gun. The gun recoils. The kinetic energy of the gun as compared to the kinetic energy of the bullet is:

A body is falling under gravity. When its speed is $v$, the rate of change of its kinetic energy is:

What is the power of a machine that does $900 \text{ J}$ of work in $18 \text{ seconds}$?

If power $P$ and work $W$ are known, what is the formula for time $t$?

$0.05 \text{ kW}$ is how many Watts?

A weightlifter lifts a mass of $100 \text{ kg}$ to a height of $2 \text{ m}$ in $5 \text{ seconds}$. What is his power? (Take $g = 10 \text{ m/s}^2$)

Which of the following is equivalent to the rate of $1 \text{ Joule}$ per $1 \text{ second}$?

An electric iron is rated $750 \text{ W}$. How much energy (in Joules) does it consume in $2 \text{ minutes}$?

What happens to the power of a machine if it performs the same work in double the time?

A motor provides $500 \text{ W}$ of power to a pump. If the pump can lift $25 \text{ kg}$ of water per second, what is the maximum height the water can reach? (Take $g = 10 \text{ m/s}^2$)

An object of mass $5 \text{ kg}$ is being pulled by a force such that its position $x$ as a function of time $t$ is $x = t^3$. The power delivered by the force at $t = 2 \text{ s}$ is:

Calculate the power of a crane that lifts a $1000 \text{ kg}$ mass at a constant speed of $12 \text{ m/min}$. (Take $g = 10 \text{ m/s}^2$)

Work is said to be zero if the angle between force and displacement is:

What happens to the Mechanical Advantage of a pulley system if more movable pulleys are added?

Mechanical Advantage ($MA$) is equal to Velocity Ratio ($VR$) when:

Tweezers are an example of which lever class?

A bottle opener acts as a Class II lever. As shown in the diagram, the distance from the fulcrum ($F$) to the load point ($L$) is $2\text{ cm}$, and the distance between the load point and the effort point ($E$) is $8\text{ cm}$. If an effort of $15\text{ N}$ is applied to the handle, what is the maximum load force that the opener can exert?

A machine with $MA = 1$ and $VR = 1$ is used to:

The $VR$ of an inclined plane making an angle $\theta$ with the horizontal is:

A compound machine is constructed using a class-II lever and a pulley system. The lever has a total length of $1.5$ m, and the load is positioned $0.3$ m from the fulcrum. The effort end of the lever is connected to a block and tackle pulley system with a velocity ratio of 3. If the overall efficiency of this compound machine is $60\%$, calculate the effort required to lift a load of $450$ N.

A $50$ kg man with a $10$ kg load on his head climbs up to the 5th floor of a building (height of each floor is $3$ m). What is the total work done? ($g = 10\, m/s^2$)

A system of pulleys has an efficiency of $80\%$. If the velocity ratio is 4, how much effort is needed to lift a load of $800$ N?

The magnitude of work done depends on:

If no force is applied to a body, the work done on it will be:

When a body falls freely under gravity, the work done by gravity is:

If the angle between the force and displacement is obtuse (more than $90^\circ$), the work done is:

A force of $10\text{ N}$ displaces an object by $10\text{ cm}$ in the direction of the force. The work done is:

Work done by a force is ________ when the force and displacement are in the same direction.

If we apply a force $F$ but the object moves in the opposite direction due to other forces, the work done by our force $F$ is:

A $1\text{ kg}$ stone is thrown from a $20\text{ m}$ high tower with a velocity of $10\text{ m/s}$ at an angle of $30^{\circ}$ with the horizontal. The work done by gravity on the stone till it hits the ground is: (Take $g = 10\text{ m/s}^2$)

A block of mass $m$ is being pulled up an inclined plane of inclination $\theta$ with a constant velocity $v$ by a force $F$ parallel to the plane. The work done by the force $F$ in time $t$ is:

If work done by a force is negative, it means that:

A girl of mass $40\ kg$ climbs a ladder. If she does $800\ J$ of work, what is the change in her energy?

Which of the following statements is true for the Work-Energy Theorem?

If an object's kinetic energy is zero, its velocity must be:

Kinetic energy of a body is $K$. If its velocity is tripled, the new kinetic energy will be:

A $20\text{ kg}$ object is lifted through a height of $2\text{ m}$. The work done against gravity is (take $g = 9.8\text{ m/s}^2$):

Work done by a force can be negative when the force acts in the ______ direction of displacement.

When the speed of a particle is tripled, its kinetic energy increases by a factor of:

If a force $F = 10 + 0.5x$ acts on a particle in the x-direction, where $x$ is in meters, find the work done by this force during a displacement from $x = 0$ to $x = 2 \text{ m}$.

A body of mass $m$ is being pulled by a string with a force $F$ such that it moves with a constant velocity $v$ on a rough horizontal surface. The work done by the string in time $t$ is:

A circular track of radius $100 \text{ m}$ is banked at an angle of $45^\circ$. If a car of mass $1000 \text{ kg}$ moves with a speed of $10 \text{ m/s}$ along the track, the work done by the normal force in one full revolution is:

Burning of a candle is an example of conversion of:

A loud speaker converts:

The capacity to do work is called:

When a ball is dropped from a height, as it falls, its:

A cyclist pedals a bicycle to power a headlight using a dynamo. The flowchart below shows the primary sequence of energy transformations that occur in this system. Which form of energy does 'X' represent?

The work done by a force can be negative if the angle between force and displacement is:

In an electric heater, which energy conversion takes place?

A body of mass $2$ kg is dropped from a height of $5$ m. What is its kinetic energy just before hitting the ground? ($g = 10$ m/s$^2$)

A person is holding a bucket by applying a vertical force of $100$ N while moving $10$ m horizontally. The work done by the person on the bucket is:

Two springs $A$ and $B$ have spring constants $k_A$ and $k_B$ such that $k_A = 2k_B$. If they are stretched by the same force, the ratio of work done on $A$ to work done on $B$ is:

An object at rest on the ground has:

Kinetic energy of an object of mass $2\text{ kg}$ moving with a velocity of $4\text{ m/s}$ is:

If an engine does $3000\text{ J}$ of work in $1\text{ minute}$, its power is:

The work done by gravity on a box being moved horizontally across a floor is:

Mechanical energy consists of both kinetic and potential energy. In a situation where friction is neglected, if kinetic energy increases, then:

Two people, A and B, do the same amount of work. If A takes $10\ s$ and B takes $20\ s$, then:

If we lift an object to a higher position, we are increasing its:

A $10 \text{ kg}$ ball is dropped from a height of $10 \text{ m}$ into a sand pile. It stops after penetrating $50 \text{ cm}$. What is the work done by the sand on the ball?

A block of mass $5 \text{ kg}$ is placed on a rough horizontal surface with coefficient of friction $0.2$. A horizontal force of $20 \text{ N}$ is applied for $10 \text{ s}$. The work done by friction is: (Take $g = 10 \text{ m/s}^2$)

If the potential energy of a particle is $U = a/x^2 - b/x$, the force acting on the particle is:

A $10\ kg$ body is moved through a distance of $2\ m$ in $2\ s$. If the force applied is $10\ N$, the power is:

One milliwatt ($mW$) is equal to:

If the time taken to do a work is very small, then the power is:

Two machines A and B have power $50\ W$ and $100\ W$ respectively. Machine B can do:

Which of the following describes the power of a machine that does $1\text{ Joule}$ of work in $1\text{ second}$?

If $1000\text{ Joules}$ of work is done in $1\text{ minute}$, the power is approximately:

An object of mass $2\text{ kg}$ falls from a height of $5\text{ m}$ to the ground in $1\text{ s}$. What is the average power exerted by gravity? (Take $g = 10\text{ m/s}^2$)

A car of mass $1000\,kg$ accelerates from rest to $30\,m/s$ in $10\,s$. What is the instantaneous power at $t=5\,s$? (Assume uniform acceleration)

An electric iron of resistance $20\,\Omega$ takes a current of $5\,A$. Calculate the energy (in $kWh$) consumed in $30\,minutes$.

A constant force $F$ is applied to a body of mass $m$ initially at rest. The power $P$ delivered to the body at time $t$ is:

Which is an example of a wheel and axle used for steering?

A bottle opener is which type of lever?

The force applied to a machine is known as the:

What is the Velocity Ratio of a wheel and axle system where the wheel radius is $R$ and the axle radius is $r$?

A person uses a ramp to load a heavy box into a truck. This ramp acts as:

Calculate the power of an engine which can lift $500\ kg$ of coal from a mine $100\ m$ deep in $10\ seconds$. (Take $g = 10\ m/s^2$)

Which of these simple machines is specifically designed to multiply the distance moved by the effort rather than the force?

The efficiency of a machine is $0.8$. If the effort moves $10\text{ m}$ while the load of $400\text{ N}$ moves $1\text{ m}$, find the effort.

In a screw jack, if the length of the handle is doubled, while keeping the pitch same, the mechanical advantage will:

A fishing rod is which class of lever?