projectile physics?

Question

A brick is thrown upwards from the top of a building at an angle of 18.9 degrees above the horizontal and with an initial speed of 21.2 m/s. (The acceleration due to gravity is 9.8 m/s^2). If the brick is in flight for 2.8 s, how tall is the building? (in meters)

Answer 1

Use the formula :

s=ut+1/2at^2

s is the height of the building, u is the initial speed, and t is the time.

But it's not a simple case of substituting all the given data on speed and time. First, solve for the time it reaches the top of its flight . Multiply this time by 2 to get the total time it takes the brick to reach the top of its flight and drop back to the level of the top of the building. Call this t'. Then you will get your time, t, in the above formula by deducting t' from 2.8s.

There's still something else. The initial speed u in the formula is the vertical component of the given speed, i.e. 21.2sin18.9. It is equal to the vertical component of the speed as the brick goes up to the top of its flight, but opposite in the direction. This is something you also have to remember: a projectile which is launched upward at a certain point will have the same same speed at the same point when it goes down, but its direction is no longer upward but downward (of course).

How to solve for t'? This time use the formula:

v=u+at, where v is the vertical component of the final speed at the top of the flight of the brick (this speed is equal to 0), u is the vertical component of the initial speed when the brick was thrown in the upward direction, a is the acceleration of gravity of 9.8m/s^2 (don't forget to put the negative sign because the brick is going against the force of gravity), and t is the time it takes the brick to reach the top of its flight.

I also suggest you make a simple diagram of the trajectory of the brick, indicating the various speeds that I told you about.

Answer 2

i have were given not were given a calculator so that you're prepared to attempt this section yet you position it up like this. First come around the time the projectile is interior the air. d=a million/2 a t squared so the a or acceleration is 9.8 the d or distance is 20.6 and the t is what you're fixing for subsequently t= the sq. root of 40-one.2 divided through utilizing 9.8. Now you realize the time so that you will be able to multiply the prev. answer circumstances 19.5. Than take that form and use the artwork formula artwork equals rigidity circumstances distance. you realize the section from the previous calculation and also you keep in mind that f=ma so 7.4 circumstances 9.80 one circumstances your previous answer supplies you the answer for section a.

Answer 3

I would say it is at least 10 feet tall, although I'm not completely sure of it.