Projectile Motion Review Homework Help

[kayjaydee]

Homework Statement

Block I of mass 4.0 kg is on a horizontal, frictionless tabletop and is placed against a spring of negligible mass and spring
constant 650 N/m. The other end of the spring is attached to a wall. The block is pushed toward the wall until the spring has been compressed a distance x, as shown above. The block is released and follows the trajectory shown, falling 0.80 m vertically and striking a target on the floor that is a horizontal distance of 1.2 m from the edge of the table. Air resistance is negligible.
a.Calculate the time elapsed from the instant block I leaves the table to the instant it strikes the floor.

b.Calculate the speed of the block as it leaves the table.

c.Calculate the distance the spring was compressed.

Homework Equations

d=volt+1/2at^2
v=vo+at
v^2=vo^2+2ad

The Attempt at a Solution

I really forgot how to do this. We are so far ahead of this unit, now, that I lost all my projectile motion mojo.
I'm guessing you solve for time using the spring constant and one of the above equations, but that's all that I know. I'm really rusty in the projectile area. :(

 

[JHamm]

Since the block leaves the table with no initial downward motion you can solve the equation
$$s = v_0t + \frac{1}{2}at^2$$
Where $s$ is the distance from the table top to the floor and $a$ is the acceleration due to gravity.
From this time you can use the same equation again using $s$ as the horizontal distance moved.
For the third part try the work energy theorem :)

 

[kayjaydee]

Okay! I think I understand now! thank you!

 

[JHamm]

No problem, good luck! :)