DYNAMICS

Newton's First law of motion is also known as law of:

Explanation:

Newton's First Law of Motion states that an object will remain at rest or in uniform motion unless acted upon by an external force. This property of objects to resist changes in their state of motion is known as inertia.

Quantity of matter contained in a body is called:

Explanation:

The quantity of matter contained in a body is known as mass. It is a measure of the amount of material in an object and is typically measured in kilograms.

Quantity of motion contained in a body is called:

Explanation:

The quantity of motion contained in a body is called momentum. It is calculated as the product of an object's mass and its velocity (\(p = mv\)).

Law of conservation of momentum defines that the total momentum of a system of two bodies before and after collision:

Explanation:

The law of conservation of momentum states that the total momentum of a closed system remains constant unless acted upon by an external force. This means the total momentum before a collision is equal to the total momentum after the collision.

Weight of a body can be measured using a spring balance, it differs from place to place because of variation in:

Explanation:

The weight of a body is the force exerted on it by gravity. Since gravitational pull varies from place to place, the weight of a body also varies. This is why a spring balance shows different readings at different locations.

It is easier to push an empty shopping cart than a full one, because the filled cart has more mass than the empty one. This can be expressed by:

Explanation:

According to Newton's Second Law, force is directly proportional to mass (\( F \propto m \)). This means that a greater mass requires a greater force to achieve the same acceleration, making it harder to push a full shopping cart compared to an empty one.

Centrifugal force is always directed:

Explanation:

Centrifugal force is an apparent force that acts outward on a body moving around a center, away from the center of the circular path. It is not a real force but a result of the inertia of the body.

Friction opposes motion between two bodies in contact because of:

Explanation:

Friction opposes motion between two bodies in contact due to the roughness of their surfaces. The microscopic imperfections on the surfaces interlock and resist the relative motion.

Which statement is true for limiting frictional force:

Explanation:

Limiting frictional force, also known as static friction, is indeed greater than rolling friction, sliding friction, and kinetic friction. It is the maximum frictional force that must be overcome to start moving an object from rest.

Force is defined as the agent that:

Explanation:

Force is defined as an agent that changes the state of rest or motion of a body. It can cause an object to accelerate, decelerate, or change direction.

Momentum is calculated as:

Explanation:

Momentum (\(p\)) is calculated as the product of an object's mass (\(m\)) and its velocity (\(v\)), i.e., \(p = mv\).

According to Newton’s second law, acceleration is produced in the direction of:

Explanation:

According to Newton’s second law, acceleration is produced in the direction of the net force acting on an object. The law is mathematically expressed as \(F = ma\), where \(F\) is the net force, \(m\) is the mass, and \(a\) is the acceleration.

Newton’s third law states that action and reaction forces are:

Explanation:

Newton’s third law states that for every action, there is an equal and opposite reaction. This means that the forces exerted by two objects on each other are always equal in magnitude and opposite in direction.

Which force is required to move a body along a circular path?

Explanation:

Centripetal force is the force required to move a body along a circular path. It acts towards the center of the circular path and is necessary to keep the object moving in a circle.

Centrifugal force is described as:

Explanation:

Centrifugal force is described as the apparent tendency of an object moving in a circular path to move away from the center of the path. It is not a real force but a result of the object's inertia.

The force resisting relative motion between two surfaces is called:

Explanation:

Friction is the force that resists the relative motion between two surfaces in contact. It acts parallel to the surfaces and opposes the motion.

Which type of friction is the strongest?

Explanation:

Static friction is the strongest type of friction. It is the frictional force that must be overcome to start moving an object from rest. Once the object is in motion, kinetic friction (which is usually less than static friction) takes over.

Why is rolling friction smaller than sliding friction?

Explanation:

Rolling friction is smaller than sliding friction because the contact area between the rolling object and the surface is smaller. In rolling friction, the object rolls over the surface, reducing the amount of friction compared to sliding, where the entire surface area is in contact.

What is the SI unit of force?

Explanation:

The SI unit of force is the Newton (N). It is defined as the force required to accelerate a one-kilogram mass by one meter per second squared (\(1 \, \text{N} = 1 \, \text{kg} \cdot \text{m/s}^2\)).

Force can act as:

Explanation:

Force can act as both a push and a pull. A push moves an object away from the source of the force, while a pull moves an object towards the source of the force.

Which statement about force is incorrect?

Explanation:

Force is a vector quantity, not a scalar quantity. This means it has both magnitude and direction. The other statements are correct: force can change an object’s shape, produce acceleration, and change an object’s state of motion.

Momentum depends on:

Explanation:

Momentum (\(p\)) depends on the mass (\(m\)) and velocity (\(v\)) of an object. It is calculated as the product of mass and velocity: \(p = mv\).

A car (mass 800 kg) moves at 2 m/s. Its momentum is:

Explanation:

The momentum (\(p\)) of the car is calculated as the product of its mass (\(m\)) and velocity (\(v\)): \(p = mv = 800 \, \text{kg} \times 2 \, \text{m/s} = 1600 \, \text{kg·m/s}\).

Which object is harder to stop if moving at the same speed?

Explanation:

An object with greater mass has greater momentum at the same speed. Therefore, a truck, which has a much larger mass compared to a cricket ball, bicycle, or tennis ball, is harder to stop if moving at the same speed.

The SI unit of momentum is:

Explanation:

The SI unit of momentum is kilogram-meter per second (kg·m/s). This is because momentum is the product of mass (in kilograms) and velocity (in meters per second).

Crumple zones in cars reduce injury risk by:

Explanation:

Crumple zones in cars are designed to absorb the energy of a collision by deforming. This increases the time over which the collision occurs, reducing the force experienced by the occupants and thus the risk of injury.

Seat belts protect passengers by:

Explanation:

Seat belts protect passengers by extending the time it takes for them to come to a stop during a collision. This reduces the force exerted on the passengers, decreasing the risk of injury.

In an isolated system, total momentum:

Explanation:

In an isolated system, the total momentum remains constant. This is known as the law of conservation of momentum, which states that the total momentum of a closed system does not change unless acted upon by an external force.

For two colliding objects, momentum before collision equals momentum after collision. This describes:

Explanation:

This describes the Law of Conservation of Momentum, which states that the total momentum of a closed system remains constant before and after a collision, provided no external forces act on the system.

If two billiard balls collide, which equation represents momentum conservation?

Explanation:

The equation \( m_1u_1 + m_2u_2 = m_1v_1 + m_2v_2 \) represents the conservation of momentum for two colliding objects. Here, \( m_1 \) and \( m_2 \) are the masses of the objects, \( u_1 \) and \( u_2 \) are their initial velocities, and \( v_1 \) and \( v_2 \) are their final velocities after the collision.

The equation \( \Delta p = Ft \) implies:

Explanation:

The equation \( \Delta p = Ft \) is derived from Newton's second law, where \( \Delta p \) is the change in momentum, \( F \) is the force, and \( t \) is the time. This equation implies that for a given change in momentum, a longer time results in a smaller force. This principle is used in designing safety features like airbags and crumple zones in cars.

Newton's First Law states that an object continues its state of rest or uniform motion unless acted upon by:

Explanation:

Newton's First Law, also known as the Law of Inertia, states that an object will remain at rest or in uniform motion in a straight line unless acted upon by an external force. This law introduces the concept of inertia, which is the resistance of an object to changes in its state of motion.

Inertia is best described as:

Explanation:

Inertia is the resistance of an object to changes in its state of rest or motion. It is a property of matter and is directly related to an object's mass. The greater the mass of an object, the greater its inertia.

According to Newton's Second Law, acceleration is:

Explanation:

According to Newton's Second Law, acceleration (\(a\)) is directly proportional to the net force (\(F\)) acting on an object and inversely proportional to its mass (\(m\)). This relationship is expressed by the equation \(F = ma\).

A force of 250 N acts on a 50 kg object. What is its acceleration?

Explanation:

Using Newton's Second Law, \(F = ma\), we can find the acceleration (\(a\)) by rearranging the equation to \(a = \frac{F}{m}\). Substituting the given values, \(a = \frac{250 \, \text{N}}{50 \, \text{kg}} = 5 \, \text{m/s}^2\).

Mass differs from weight because:

Explanation:

Mass is a measure of the amount of matter in an object and is constant regardless of location. Weight, on the other hand, is the force exerted on an object by gravity and varies depending on the gravitational pull at different locations.

Newton's Third Law states that action and reaction forces are:

Explanation:

Newton's Third Law states that for every action, there is an equal and opposite reaction. This means that the forces exerted by two objects on each other are always equal in magnitude and opposite in direction, but they act on different objects.

When a rocket accelerates upward, the exhaust gases push:

Explanation:

When a rocket accelerates upward, the exhaust gases are expelled downward, pushing against the rocket. According to Newton's Third Law, the rocket exerts a force on the gases, and the gases exert an equal and opposite force on the rocket, propelling it upward.

What keeps water in a vertically rotating bucket from spilling?

Explanation:

When a bucket of water is rotated vertically, the water tends to move outward due to centrifugal force, which is an apparent force acting away from the center of rotation. This force keeps the water pressed against the bottom of the bucket, preventing it from spilling.

Centripetal force acts:

Explanation:

Centripetal force is the force that acts toward the center of a circular path, keeping an object moving in that path. It is necessary for circular motion and is directed inward, perpendicular to the velocity of the object.

Which formula correctly represents centripetal force?

Explanation:

The formula for centripetal force is \( F = \frac{m v^2}{r} \), where \( F \) is the centripetal force, \( m \) is the mass of the object, \( v \) is the velocity of the object, and \( r \) is the radius of the circular path.

A cyclist of mass 60 kg moves in a circle of radius 20 m at 5 m/s. What is the centripetal force?

Explanation:

Using the formula for centripetal force \( F = \frac{m v^2}{r} \), we substitute the given values: \( m = 60 \, \text{kg} \), \( v = 5 \, \text{m/s} \), and \( r = 20 \, \text{m} \). Thus, \( F = \frac{60 \times 5^2}{20} = \frac{60 \times 25}{20} = 75 \, \text{N} \).

Centrifugal force is:

Explanation:

Centrifugal force is an apparent force that acts outward from the center of rotation in a circular path. It is not a real force but a result of the inertia of the object moving in the circular path.

Which application uses centrifugal force to separate particles?

Explanation:

A centrifuge is a device that uses centrifugal force to separate particles of different densities. By spinning a mixture at high speeds, the denser particles move outward, separating from the less dense particles.

Why are roads banked at curves?

Explanation:

Roads are banked at curves to provide the necessary centripetal force for vehicles to navigate the curve safely. The banking helps to counteract the centrifugal force acting on the vehicle, reducing the reliance on friction between the tires and the road.

In a cream separator, where do heavier particles move?

Explanation:

In a cream separator, the heavier particles move toward the walls due to the centrifugal force acting on them. This force pushes the denser particles outward, separating them from the lighter particles.

What principle dries clothes in a washing machine’s dryer?

Explanation:

The drying principle in a washing machine’s dryer involves centrifugal force. As the drum spins, the water in the clothes is thrown outward due to centrifugal force, effectively removing the water from the clothes.

Which factor does NOT affect centripetal force?

Explanation:

Centripetal force is given by the formula \( F = \frac{m v^2}{r} \), where \( m \) is the mass of the object, \( v \) is the velocity, and \( r \) is the radius of the circular path. Acceleration due to gravity does not affect centripetal force.

Centrifugal force has the same magnitude as centripetal force but acts:

Explanation:

Centrifugal force has the same magnitude as centripetal force but acts in the opposite direction. While centripetal force acts toward the center of the circular path, centrifugal force acts outward from the center.

What is separated using a gas centrifuge?

Explanation:

A gas centrifuge is used to separate isotopes, which are atoms of the same element with different masses. The centrifuge spins at high speeds, causing the heavier isotopes to move outward, separating them from the lighter isotopes.

What is the primary cause of friction between two surfaces?

Explanation:

The primary cause of friction between two surfaces is the roughness or deformation of the surfaces. When two surfaces come into contact, the microscopic imperfections on the surfaces interlock and resist the relative motion, causing friction.

Frictional force acts in a direction:

Explanation:

Frictional force acts in a direction opposite to the applied force. It opposes the relative motion between two surfaces in contact, making it harder to move objects.

The force that resists relative motion between two surfaces is called:

Explanation:

Friction is the force that resists the relative motion between two surfaces in contact. It acts parallel to the surfaces and opposes the motion.

The relationship between limiting friction (F) and normal reaction (R) is:

Explanation:

The relationship between limiting friction (\(F\)) and normal reaction (\(R\)) is given by \( F = \mu R \), where \( \mu \) is the coefficient of friction. This equation shows that the maximum static friction is directly proportional to the normal force.

Which type of friction is the strongest?

Explanation:

Rolling friction is smaller than sliding friction because:

Explanation:

Rolling friction is smaller than sliding friction because the contact area between the rolling object and the surface is reduced. In rolling friction, the object rolls over the surface, reducing the amount of friction compared to sliding, where the entire surface area is in contact.

Ball bearings in machines help reduce friction by:

Explanation:

Ball bearings in machines help reduce friction by converting sliding friction into rolling friction. Rolling friction is generally smaller than sliding friction, making it easier to move parts and reducing wear and tear.

The Anti-lock Braking System (ABS) in vehicles maintains:

Explanation:

The Anti-lock Braking System (ABS) in vehicles maintains static friction between the tires and the road. By preventing the wheels from locking up, ABS ensures that the tires continue to roll, maintaining static friction, which provides better control and shorter stopping distances.

Which is an advantage of friction?

Explanation:

One advantage of friction is that it enables walking. Friction between the soles of our shoes and the ground provides the necessary grip to walk without slipping.

Throwing sand on railway tracks during rain helps:

Explanation:

Throwing sand on railway tracks during rain helps increase friction between the wheels of the train and the tracks. This added friction improves the grip and prevents the wheels from slipping, especially when the tracks are wet and slippery.

Which material has the lowest coefficient of friction?

Explanation:

Ice on ice has the lowest coefficient of friction among the given options. The smooth and slippery surface of ice results in very low friction, making it easy for objects to slide over it.

A major disadvantage of friction is:

Explanation:

A major disadvantage of friction is the wastage of energy. Friction converts some of the useful mechanical energy into heat, which is often dissipated and not utilized, leading to energy loss.

Lubricants like oil reduce friction by:

Explanation:

Lubricants like oil reduce friction by forming a slippery layer between two surfaces in contact. This layer separates the surfaces, reducing the direct contact and thus the friction between them.

What is "limiting friction"?

Explanation:

Limiting friction, also known as maximum static friction, is the maximum frictional force that must be overcome to start moving an object from rest. Once this force is exceeded, the object begins to move, and kinetic friction takes over.

Why does a rolling ball eventually stop?

Explanation:

A rolling ball eventually stops due to the frictional force acting on it. Friction opposes the motion of the ball, gradually reducing its velocity until it comes to a stop.

Grooves on tires are designed to:

Explanation:

Grooves on tires are designed to improve grip via friction. The grooves help channel water away from the contact surface, increasing the friction between the tires and the road, especially in wet conditions.

The normal reaction force (R) equals an object’s weight when it is:

Explanation:

The normal reaction force (\(R\)) equals an object’s weight when it is on a horizontal surface. In this case, the normal force balances the weight of the object, keeping it in equilibrium.

Kinetic friction acts when an object is:

Explanation:

Kinetic friction acts when an object is moving. It is the frictional force that opposes the relative motion between two surfaces in contact and is generally less than static friction.