Newtonian Mechanics

Question 1

Define speed

Answer 1

Speedis the distance travelled per unit time.

Question 2

Define velocity

Answer 2

Velocity is rate of change of displacement

Question 3

Define acceleration

Answer 3

Acceleration is the rate of change of
velocity.

Question 4

What affects air resistance?

Answer 4

• density of air
• cross-sectional area of the object
• velocity of the object

Question 5

What is mass? (and what do we use to measure it?)

Answer 5

• Mass is the amount of matter in a body
• Using a beam balance or a calibrated electronic mass balance.

Question 6

What is weight? (and what do we use to measure it?)

Answer 6

• Weight is the amount of gravitational force acting on a body.
• can be measured using a Spring/Newton Balance

Question 7

Formula for Weight.

Answer 7

W = m (mass) x g (gravitational field)

Question 8

What is gravitational field?

Answer 8

Gravitational fieldis the region in which a mass experiences a force due to gravitational attraction.

Question 9

1. What is gravitational field strength?
2. What is the gravitational field strength for earth and moon?

Answer 9

• Gravitational field strength,g, is the gravitational force acting per unit mass
• Earth is 10N/kg. Moon is 1.6N/kg

Question 10

State the Newton’s 1st Law.

Answer 10

An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force

Question 11

State Newton’s 2nd Law.

Answer 11

When a resultant force acts on an object of a constant mass, the object will accelerate in the direction of force.

Question 12

State Newton’s 3rd Law.

Answer 12

Forces always occur in (action-reaction) pairs.

Question 13

Formula for resultant force.

Answer 13

F (resultant force) = m (mass) x a (acceleration)

Question 14

What is inertia?

Answer 14

Inertia is the reluctance of a body to change its state of rest or motion.

Question 15

How does wheels reduce friction?

Answer 15

The circular shape of the wheels reduces the area in contact with the surface.

Question 16

How does ball bearings reduce friction?

Answer 16

They roll around and prevent surfaces from coming in contact directly or rubbing with each other

Question 17

How does lubricant and polished surfaces reduce friction?

Answer 17

These smooth or remove the surface’s
irregularities

Question 18

Define moment.

Answer 18

The moment is the product of the force and the perpendicular distance from pivot to line of action of force.

Question 19

State the principle of moments.

Answer 19

For a body in an equilibrium , the total sum of clockwise moments about any point is equal to the total sum of anti-clockwise moments about the same point.

Question 20

Formula for moments.

Answer 20

Moment = F (force) × d (perpendicular distance between force and pivot)

Question 21

Define center of gravity.

Answer 21

The centre of gravity of an object is a point where all the weight of the object appears to act on, regardless of its orientation.

Question 22

How to find the center of gravity of any irregular and flat objects like cardboards?

Answer 22

1. Make at least 3 holes at different locations on the cardboard.
2. Suspend cardboard through one of the holes using a pin, such that it hangs freely and come to rest.
3. Attach the plumbline to the pin. Indicate on the cardboard the vertical line made by the plumbline.
4. Repeat for the other holes.
5. The point of intersection of the lines is the centre of gravity of this irregularly shaped cardboard.

Question 23

Define pressure

Answer 23

Pressure is defined as the force acting per unit area.

Question 24

Define efficiency

Answer 24

The fraction of the useful power output over the total energy input as a percentage

Question 25

Why does velocity changes when a car is spinning in circles?

Answer 25

Velocity changes as direction of motion changes as it spins

Question 26

Why is liquids used over gases in pistons?

Answer 26

Liquids are incompressible and can transmit pressure uniformly through liquid