Contact and Non-contact Forces

What are the main types of contact forces?

• 1. 1. Magnetic force

• 1. 2. Centripetal force

• 1. 3. Frictional force, normal force, tension force, applied force

• 1. 4. Gravitational force

Answer explanation

The main types of contact forces include frictional force, normal force, tension force, and applied force. These forces act through direct contact between objects, unlike gravitational and magnetic forces, which are non-contact forces.

Define friction and its role in motion.

• 1. 1. Friction is the opposing force between surfaces that enables control in motion.

• 1. 2. Friction is a force that increases speed in motion.

• 1. 3. Friction has no effect on the movement of objects.

• 1. 4. Friction is the force that allows objects to float in the air.

Answer explanation

Friction is the opposing force between surfaces that enables control in motion. It allows objects to start, stop, and change direction, making it essential for movement, unlike the other options which misrepresent its role.

What is the difference between static and kinetic friction?

• 1. 1. Static friction acts on moving objects while kinetic friction does not.

• 1. 2. Kinetic friction only occurs when objects are at rest.

• 1. 3. Static friction prevents motion; kinetic friction opposes motion.

• 1. 4. Static friction is always greater than kinetic friction.

Answer explanation

Static friction prevents motion between surfaces at rest, while kinetic friction acts on surfaces in motion, opposing their movement. Thus, the correct choice highlights this fundamental difference.

Choose three examples of noncontact forces.

• 1. 1. Gravitational force, magnetic force, electric force

• 1. 2. Normal force

• 1. 3. Frictional force

• 1. 4. Tension force

Answer explanation

Noncontact forces act at a distance without physical contact. Gravitational, magnetic, and electric forces are examples of such forces, while normal, frictional, and tension forces require contact between objects.

What is Newton's First Law of Motion?

• 1. 1. An object will accelerate unless a force is applied.

• 1. 2. An object will remain at rest or in uniform motion unless acted upon by an external force.

• 1. 3. An object will remain in motion only if it is on a flat surface.

• 1. 4. An object will change its motion only if it is in a vacuum.

Answer explanation

Newton's First Law states that an object will remain at rest or in uniform motion unless acted upon by an external force. This means that without a force, an object's state of motion will not change.

What does Newton's Second Law of Motion state?

• 1. 1. The acceleration of an object is constant regardless of the net force applied.

• 1. 2. An object in motion will stay in motion unless acted upon by an equal force.

• 1. 3. The force acting on an object is equal to its mass multiplied by its velocity.

• 1. 4. The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

Answer explanation

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass, which is accurately described in the correct choice.

Which of the statements describes Newton's Third Law of Motion?

• 1. 1. An example of this law is when a swimmer pushes the water backwards with their hands; the water pushes the swimmer forward with an equal force, allowing them to move through the water.

• 1. 2. A ball rolls down a hill due to gravity acting on it.

• 1. 3. A car accelerates forward when the driver presses the gas pedal.

• 1. 4. A rocket launches into space by pushing against the ground.

Answer explanation

Newton's Third Law states that for every action, there is an equal and opposite reaction. The swimmer pushing water back exemplifies this, as the water exerts an equal force forward, propelling the swimmer.

How does gravitational force affect objects on Earth?

• 1. 1. Gravitational force causes objects to be pulled towards the Earth, giving them weight and affecting their motion.

• 1. 2. Gravitational force has no effect on the motion of objects on Earth.

• 1. 3. Gravitational force only affects objects in space, not on Earth.

• 1. 4. Gravitational force pushes objects away from the Earth, causing them to float.

Answer explanation

Gravitational force pulls objects towards the Earth, which gives them weight and influences their motion. This is why we observe objects falling or staying grounded, confirming the correct choice.

What is the formula for calculating gravitational force?

• 1. A) F = m1 * m2 / r

• 1. B) F = G * (m1 + m2) * r

• 1. C) F = G * m1 * m2 * r^2

• 1. D) F = G * (m1 * m2) / r^2

Answer explanation

The correct formula for gravitational force is F = G * (m1 * m2) / r^2, where G is the gravitational constant, m1 and m2 are the masses, and r is the distance between their centers. This reflects Newton's law of universal gravitation.

Explain how electromagnetic forces operate between charged particles.

• 1. 1. Electromagnetic forces operate between charged particles through attraction and repulsion governed by their electric fields, as described by Coulomb's law.

• 1. 2. Charged particles do not interact through electromagnetic forces.

• 1. 3. Electromagnetic forces only attract neutral particles.

• 1. 4. Electromagnetic forces are only relevant at very high speeds.

Answer explanation

Electromagnetic forces between charged particles arise from their electric fields, leading to attraction or repulsion as described by Coulomb's law. This is the fundamental principle governing their interactions.