PHY 26

What is meant by free fall

Free fall is motion with acceleration due to gravitational force only

Without air resistance so it is vacuum

Distance

Length of path taken

Displacement

Distance of an object from a point in a certain distance

Distance compared to displacement

Distance is always longer than displacement

Speed

Rate of change of distance

Velocity

Rate of change in displacement

Acceleration

Rate of change in velocity

Friction compensated runway

A runway that is tiler slightly so that the component of gravity acting on slope cancels out the frictional force acting against motion

What does each dot on ticker tape mean?

A fixed time interval

Newton’s first law (Inter

Tendency of an object to remain at rest or in uniform motion at uniform velocity unless acted upon by an unbalanced external force

Newton’s Law of Gravitation formula

F = G(m1m2) / r²

What does F represent in Newton’s Universal Law of Gravitation?

Gravitational force of attraction between two objects (N)

What does m1m2 represent in Newton’s Universal Law of Gravitation?

The product of masses of 2 objects

What does r represent in Newton’s Universal Law of Gravitation?

The square distance between the centre of mass of 2 objects

Is gravitational force attractive or repulsive?

Attractive (never repulsive)

What is the inference of the effects of mass and distance between 2 objects on gravitational force?

Gravitational force between two bodies depends on the mass of the bodies, as well as the distance between them

Formula of centripetal force

F = mv² / r

What is the direction of centripetal force

Towards the centre of the circle

Tensions force in Centripetal

T = Fc

Formula of gravitational acceleration

g = GM / r²

Formula of centripetal acceleration

a = v² / r

Formula of orbital period if mass is given (Newton)

T = 2pi square root (r³ / GM)

Formula of orbital period if mass is NOT given (Kepler)

T1² / T2² = r1³ / r2³

Orbital velocity from circumference and period (if period is given)

v = 2pi r / T

Orbital velocity from gravitation (if mass of central body is given)

v = square root (GM / r)

Formula for escape velocity

Ve = square root (2GM / r)

Kepler’s first law (Law of Orbits)

The orbit of every planet is an ellipse, with the Sun located at one of the two foci

Kepler’s second law (Law of Areas)

A line that connects a planet to the Sun sweeps up equal area in equal time

Kepler’s third law (Law of periods)

The square orbital period of a planet is directly proportional to the cube of the radius of its orbit

What is the principle of conservation of momentum?

The total momentum before a collision / explosion is the same as the total momentum after the collision / explosion

Elastic collision

Objects move separately after the collision, where total kinetic energy and momentum is conserved

• bouncing ball off the wall

Inelastic collision

Objects move together after the collision, where kinetic energy and momentum is not conserved

• car collision where cars stick together after collision (some of the KE is converted into heat and sound energy)

Explosion

Objects are stationary and acts as one body before explosion, objects move apart after the explosion, kinetic energy is not conserved

• launching of rocket

• Firing of gun

Newton’s Second Law (F = ma)

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

What is impulse

Change in momentum

What is weight

Force exerted on an object due to gravitational pull

Principle of conservation of momentum

Total momentum before collision is equal to the total momentum after collision if no external force is acting on it

Newton’s third law

For every action there is a reaction of equal magnitude but in the opposite direction

Safety features of cars to reduce impulsive force

Prevention seatbelt, airbag, crumple zone, anti lock breaking system

How to decrease impulsive force

Extending the impact time

Geostationary satellite

Appears to stay above the same point on ea

What is meant by escape velocity

Minimum velocity needed by an object to overcome gravitational force of a celestial body to escape into outer space