Forces

What is the basic definition of a force as described in this video?

• A change in velocity

• A push or a pull

• A type of energy

• A form of matter

Answer explanation

A force is defined as a push or a pull that can cause an object to change its motion. This definition highlights the fundamental nature of forces in physics.

Which of the following is a vector quantity according to this video?

• Mass

• Force

• Temperature

• Time

Answer explanation

Force is a vector quantity because it has both magnitude and direction, unlike mass, temperature, and time, which are scalar quantities that only have magnitude.

In the context of this video, what does it mean when the net force on an object is zero?

• The object is accelerating

• The object is at rest or moving at a constant velocity

• The object is changing direction

• The object is gaining mass

Answer explanation

When the net force on an object is zero, it means there is no change in its motion. Therefore, the object is either at rest or moving at a constant velocity, as per Newton's first law of motion.

What unit is used to measure force, as mentioned in this video?

• Joules

• Watts

• Newtons

• Pascals

Answer explanation

The unit used to measure force is Newtons. Joules measure energy, Watts measure power, and Pascals measure pressure. Therefore, the correct answer is Newtons.

According to this video, which force is described as a non-contact force?

• Friction

• Drag

• Gravity

• Tension

Answer explanation

Gravity is a non-contact force because it acts at a distance, pulling objects toward each other without direct physical contact. In contrast, friction, drag, and tension require contact between surfaces or objects.

What happens to the forces acting on Tim and Moby when they reach terminal velocity during freefall?

• The forces become unbalanced

• The net force becomes zero

• The gravitational force increases

• The drag force disappears

Answer explanation

When Tim and Moby reach terminal velocity, the upward drag force equals the downward gravitational force. This results in a net force of zero, meaning they stop accelerating and fall at a constant speed.

Which of the following best describes the role of friction as mentioned in this video?

• It accelerates objects

• It resists motion between surfaces

• It increases the speed of objects

• It acts only in liquids

Answer explanation

Friction is a force that opposes the relative motion of surfaces in contact. Therefore, the correct choice is that it resists motion between surfaces, as it slows down or prevents movement.

What is the effect of pulling the parachute cord on the forces acting on Tim and Moby?

• It decreases drag

• It creates an unbalanced force upward

• It increases gravitational force

• It eliminates air resistance

Answer explanation

Pulling the parachute cord increases the surface area, creating more drag. This results in an unbalanced force upward, counteracting gravity and slowing Tim and Moby's descent.

How does this video describe the relationship between engine force and friction/drag when the plane is moving at a constant speed?

• Engine force is less than friction and drag

• Engine force is greater than friction and drag

• Engine force is equal to friction and drag

• Engine force is unrelated to friction and drag

Answer explanation

The video explains that when a plane moves at a constant speed, the engine force must balance out the friction and drag. Therefore, engine force is equal to friction and drag, ensuring no acceleration occurs.

What is the significance of Isaac Newton in the context of this video?

• He invented the airplane

• He discovered the concept of drag

• He developed the laws of motion and the unit of force is named after him

• He was the first person to skydive

Answer explanation

Isaac Newton is significant for developing the laws of motion, which are fundamental to physics. The unit of force, the Newton, is named in his honor, highlighting his impact on our understanding of motion and forces.