Newtonian Mechanics Flashcards
Define speed
Speedis the distance travelled per unit time.
Define velocity
Velocity is rate of change of displacement
Define acceleration
Acceleration is the rate of change of
velocity.
What affects air resistance?
- density of air
- cross-sectional area of the object
- velocity of the object
What is mass? (and what do we use to measure it?)
- Mass is the amount of matter in a body
- Using a beam balance or a calibrated electronic mass balance.
What is weight? (and what do we use to measure it?)
- Weight is the amount of gravitational force acting on a body.
- can be measured using a Spring/Newton Balance
Formula for Weight.
W = m (mass) x g (gravitational field)
What is gravitational field?
Gravitational fieldis the region in which a mass experiences a force due to gravitational attraction.
- What is gravitational field strength?
- What is the gravitational field strength for earth and moon?
- Gravitational field strength,g, is the gravitational force acting per unit mass
- Earth is 10N/kg. Moon is 1.6N/kg
State the Newton’s 1st Law.
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
State Newton’s 2nd Law.
When a resultant force acts on an object of a constant mass, the object will accelerate in the direction of force.
State Newton’s 3rd Law.
Forces always occur in (action-reaction) pairs.
Formula for resultant force.
F (resultant force) = m (mass) x a (acceleration)
What is inertia?
Inertia is the reluctance of a body to change its state of rest or motion.
How does wheels reduce friction?
The circular shape of the wheels reduces the area in contact with the surface.
How does ball bearings reduce friction?
They roll around and prevent surfaces from coming in contact directly or rubbing with each other
How does lubricant and polished surfaces reduce friction?
These smooth or remove the surface’s
irregularities
Define moment.
The moment is the product of the force and the perpendicular distance from pivot to line of action of force.
State the principle of moments.
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.
Formula for moments.
Moment = F (force) × d (perpendicular distance between force and pivot)
Define center of gravity.
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.
How to find the center of gravity of any irregular and flat objects like cardboards?
- Make at least 3 holes at different locations on the cardboard.
- Suspend cardboard through one of the holes using a pin, such that it hangs freely and come to rest.
- Attach the plumbline to the pin. Indicate on the cardboard the vertical line made by the plumbline.
- Repeat for the other holes.
- The point of intersection of the lines is the centre of gravity of this irregularly shaped cardboard.
Define pressure
Pressure is defined as the force acting per unit area.
Define efficiency
The fraction of the useful power output over the total energy input as a percentage
