You replace a 200 W lamp with a more efficient 55 W LED lamp. If you leave your lights on 24 hours a day, how much energy are yo
2 answers:
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Answer:
I don't know if it is correct or not.
Answer:
3. 0.5 sec.
Explanation:
A bullet fired horizontally follows a projectile motion, which consists of two independent motions:
- A horizontal motion with constant speed
- A vertical motion with constant acceleration, g = 9.8 m/s^2, towards the ground
The time taken for the bullet to reach the ground can be calculated just by considering the vertical motion:
where y is the vertical position at time t, h is the initial height, and is the initial vertical velocity of the bullet.
Since the bullet is fired horizontally, . So the equation becomes
And the time that the bullet takes to reach the ground can be found by requiring y=0 and solving for t:
As we can see, in this equation there is no dependance on the initial speed of the bullet: therefore, if the bullet is fired still horizontally but with a different speed, it will still take the same time (0.5 s) to reach the ground.