mechanics

Question 1

Distinguish between a vector and scalar?

Answer 1

A vector has magnitude and direction. A scalar has magnitude and no direction.

Question 2

Which of the following are vector quantities?

Answer 2

Force, momentum.

Question 3

Define velocity?

Answer 3

Velocity is speed in a given direction. It is the rate of change of displacement. Formula: v = s / t, where s = distance and t = time.

Question 4

What quantity is defined as the rate of change of velocity?

Answer 4

Acceleration.

Question 5

Define acceleration?

Answer 5

Acceleration is the rate of change of velocity. Formula: a = (v – u) / t, where u = initial velocity, v = final velocity, and t = time in seconds.

Question 6

Define displacement?

Answer 6

Displacement is distance in a given direction. It is a vector.

Question 7

What is work (Joule)?

Answer 7

Work is done when a force moves a body through a distance (displacement). Work = Force × Displacement (W = F × s).

Question 8

Name the SI unit of measurement defined as the work done when a Force of one newton moves its point of application one metre in the direction of the force. What quantity, other than work, is also measured using this unit?

Answer 8

Joule (J). Other quantities measured using this unit include kinetic energy, potential energy, and food energy.

Question 9

Define power?

Answer 9

Power is the rate of doing work. Formula: P = E / t, where E = Energy and t = time in seconds.

Question 10

Define the unit of power (the watt)?

Answer 10

One watt is one joule per second. Formula: P = E / t, where E = Energy and t = time in seconds.

Question 11

Define mass?

Answer 11

Mass is the amount of matter in a body and a body’s ability to resist motion. Mass is a scalar.

Question 12

Define weight (force due to gravity)?

Answer 12

Weight is the product of mass and acceleration due to gravity. Formula: W = mg, where m = mass and g = acceleration due to gravity. Weight is a vector.

Question 13

Define force?

Answer 13

Force causes a mass to accelerate or changes a body’s motion or direction. Formula: F = ma, where m = mass and a = acceleration.

Question 14

Define the unit of force, the newton?

Answer 14

One newton gives a mass of 1 kilogram an acceleration of 1 metre per second squared.

Question 15

Define momentum?

Answer 15

Momentum is the product of mass and velocity. Formula: p = m × v.

Question 16

State the principle of conservation of momentum?

Answer 16

In a closed system with no external force, the total momentum before is equal to the total momentum after. Formula: m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂.

Question 17

Define potential energy?

Answer 17

Potential energy is energy due to position. Formula: E = mgh.

Question 18

Define potential and kinetic energy?

Answer 18

Potential energy is energy due to position. Formula: E = mgh. Kinetic energy is energy due to motion. Formula: E = 1/2mv².

Question 19

What is the relationship between the potential energy and the kinetic energy of an object falling freely?

Answer 19

Potential energy equals kinetic energy. Energy = mgh = 1/2mv².

Question 20

State the principle of conservation of energy?

Answer 20

Energy is neither created nor destroyed, but can be converted from one form to another. Total energy is constant in a closed system.

Question 21

State Newton’s first law of motion?

Answer 21

An object remains at constant velocity or speed in a straight line unless acted upon by an external force.

Question 22

State Newton’s second law of motion?

Answer 22

The rate of change of momentum is proportional to the force applied and in the same direction as the applied force. Formula: F ∝ (mv - mu) / t.

Question 23

State Newton’s third law of motion?

Answer 23

For every action, there is an equal and opposite reaction.

Question 24

What is the relationship between G, the gravitational constant, and g, the acceleration due to gravity?

Answer 24

g = GM / r².

Question 25

State Newton’s law of gravitation?

Answer 25

The force is proportional to the product of two masses and inversely proportional to the square of the distance between them. Formula: F = Gm₁m₂ / r².