Acceleration near Earth's surface

If something is accidentally dropped, you directly experienced how significant the effect of gravity is.

Acceleration due to gravity

Acceleration due to gravity is the acceleration occurring when an object can freely. Acceleration's symbol due to gravity is 'g'. Physicists have found that the average g value measured very close to Earth's surface is 9.8 m/s2. Different pales on Earth have different g values, like in Mexico City is a bit lower than the average of 9.8 m/s2 as the city has a high elevation and thus is farther from Earth's center, which had an cool effect in 1968 Summer Olympic Games, held there. Many high, long jumps, and pole-vaulting records were broken during these attributed in part to lower g values. The 'g' value is different on other planets and celestial objects.

Uniform vertical acceleration

All objects moving freely in a vertical direction experience acceleration due to gravity (g).

The 5 key motion equations earlier are used to show how gravity affects objects moving vertically.

Problem 1

A flowerpot is knocked off a window, which is 10 m above the ground without air resistance. 

How long does it take the pot to reach the ground?

Solution: 

It can be said that the flowerpot was initially at rest, so its velocity is 0 m/s.

   →                                

• Δd =  -100 m 

   →

• a = g = -9.8 m/s2; 

    →

• vi = 0 m/s (recall that no air resistance = 9.8 m/s2) 

• Required: Δt

Since displacement, acceleration, and initial velocity of the pot is given, use Equation 3 of the 5 key motion

                                                                  →     →                    →

equations to solve for time: Δd = viΔt + 1/2 a(Δt)2.

See that the given displacement and acceleration values are both negative, as both vectors point downward.

Subproblem 1

What's the final velocity (vf) of the flowerpot? 

Solution:

Vehicule safety

Advanced car technologies saved many lives. Since 1987 the Canadian number of car accident deaths dropped by 33%. 

Speeding is a major factor in 30% of all fatal crashes. Stats show that teens are less likely to wear seat belts than other ages. Speed also affect the emissions released by cars and their efficiency. Car emissions make up a substantial portion of greenhouse gas emissions. Even a highly fuel-efficient car is at its most efficient when driven at reduced speed. Transport Canada shows that by reducing a car's speed from 120 km/h to 100 km/h, fuel consumption can drop by 20%. A speed limiter is an electronic device limiting a car from a certain speed, to increase safety and reduce environmental impact of truck emissions.a