[ariel1014]

Four seconds after starting from rest, what will be the velocity or speed of a freely faling object?

[ariel1014]

An object falls freely for 12 seconds.

a) Calculate the velocity or speed after 12 seconds.

b) Calculate the distance fallen after 12 seconds.

[Capuchin]

Let's see if I can help you with a fundamental understanding of what you've been asked to do here.

You want to find the speed in meters per second.

You know the gravitational acceleration on earth is g which is 9.8 meters per second per second

What this acceleration means is that (provided that there are no other forces, which is what "free fall" means) every second, the speed increases by 9.8 meters per second.

Now, can you complete the logic to answer your question?

[ariel1014]

An automobile increases speed from 20km/hr to 80km/hr in 6.0 seconds. What is the acceleration.

[Capuchin]

For the distance fallen, you will need one of your suvat equations.

For the accelerating car you must realise that the acceleration is simply the change in speed over the amount of time it takes to make that change. (this is only average acceleration)

[jiten55]

Free Fall:

Use the following formula for velocity:

v = u + at

v = final velocity u = initial velocity = 0

a = acceleration = g, t = time

For distance: Formula is

s = ut + 1/2 at^2

where s is distance.

[jiten55]

For the automobile :

Acceleration is rate of change of velocity.

In this case:

Average acceleration = (Final Velocity - Initial Velocity)/Time

[kesavan]

using v=u+at
v=gt
where g-gravitational acceration
t- time (4s)
v=10*4=40 ms^-1