this should be pretty easy for most of you. Okay…if you are travelling down the highway at 70 mph in your vehicle, and you drop a ball out your window, will the ball land directly on the spot that you dropped it over, or will it’s forward momentum carry it past that spot. I guess this would be the same as dropping a bomb on a target. Do they wait until they are directly over the target, or do they have to release it before they get over the target? I think that it should keep going a little since it has forward momentum. If not, please let me know why. thanks
Ignoring air resistance, it would move along with the car and hit the ground right next to the car. A body in motion tends to stay in motion.
does everybody agree with this? I know i do. but I am trying to prove somebody wrong here, and they still don’t believe it. haha
That’s correct. From what I remember from my high skool fiziks, as long as the dropped body has some forward momentum, the path of it’s fall will appear curved to an observer standing on the side of the road. ie: it will continue to travel forward past the point of release and hit the ground a little further on. (How much further depends on the speed of the car)
Look at it this way: You are in a car going 60 mph and you toss a ball in the air and catch it. It takes one second between toss and catch. Does the ball slam into your chest the instant you toss it in order to land over the same spot of road you were at when you released the ball? Of course not. You, the ball, and the car are all traveling down the road at 60 mph and the ball lands in your hand 88 ft down the road from where you tossed it into the air.
I agree! 
It’s non-intuitive, I’ll grant. Our physical intuition might lead us to suspect something like: “An object in motion will tend to slow down and stop unless something keeps pushing it.”
Hell, it seems to be true if you do a few simple observations or even some crude experiments. When we roll something along the ground, it eventually stops. Unfortunately, we’re sort of stuck in a special case of Newtonian mechanics - we (generally) can’t escape frictional forces.
If you could somehow do the car experiment in a vacuum, when you dropped the ball out the window it would keep moving right along with you - it would fall downwards, but it’d keep moving sideways at 70 mph. Friction (which does tend to cause relative motion to go to zero) with the air is the only reason that the ball would slow down.
Air resistance can do weird things. When dropped in a vacuum, a feather and a brick fall side by side, neither outpacing the other. There are science education videos out there doing just that experiment in a bell jar - it’s freaky to see.
The ball does indeed move with the car. Horizontal motion is completely independant of vertical motion. By the way, regarding bombers: Back in the day, if you wanted to drop a bomb on someone, the bomb guy in the back of the plane would calculate the time it would take the bomb to fall (based on the altitude and acceleration due to gravity, which is -9.8m/s[sup]2[/sup].) and then figure out where to drop it so it lands on the target. Assuming the plane continues to fly straight forward, the plane will be directly over the target when the bomb hits.
Nowadays, them newfangled computers figure this stuff out automagically.
Also… since you brought up Bombs:
I talked with a retired Major from the 91st Bombergroup. He was a lead bombardier in WWII and dropped many bombs over Europe.
Each bomb has a ballistic coefficient that is plugged into their equations to find the right release point. Other data includes the speed and hieght of the planes. The bombs leave the plane going the exact same speed of the plane, and falling at 9.8m/s/s. The wind then starts to slow the bomb down a bit so it is no longer moving as fast as the plane. The bombs are dropped well before the target is under the planes.
I don’t know if I explained that very well… but basically your friend is wrong.
In the B-17s the bombardier was in the front, under the pilots.
-Just sharing…
former Physics teacher checking in.
recall that the ball, still in your hand outside the car window, has an initial velocity in the X direction (X being the direction of travel). It has no initial velocity in the Y (downward) direction, because you’re still holding it!!
Plug in Newton’s first law…<here>. When you let go, the ball would hover at that level, b’cept there’s now a FORCE acting on the ball (only forces can accelerate masses). Thus, the ball changes it’s velocity (accelerates) and “speeds up” as it goes downward.
Wait!!! let’s not forget about the X direction stuff. When held in your hand, the ball did have an initial velocity int he X direction; it was the same as the velocity of the car. When you let go, the ball will continue to have that velocity until a force acts on the ball to change it’s velocity (only forces can accelerate masses). Hmmmm… What force is acting in the + or - X direction? Barring air resistance (a friction force) NONE!! Ergo the ball will continue in the X direction, with the same velocity as the car until it hit’s the ground. QED
NB: By WWII bomb sights were compensated for altitude, air speed etc. This is why, in war movies, the bombadier always asked for a check of altitude and airspeed (and then turned the little nobs on the sights) before releasing bombs.
IIRC, the image of a bombardier holding the bomb release in one hand, looking through the bomb sight, pressing the button, and then seeing the bombs fall out of the bomb bay is a bit of Hollywood fiction. At least as it pertains to the Norden bomn site. Again IIRC, the bombardier flew the aircraft on the final bomb run and set the parameters (altitude, speed, crosswind, etc.) on the Norden bomb site. Once everything was set, the bombardier just held the aircraft steady or it was on autopilot (I don’t recall which). When two needles came together in the bombsite, the bombs would release automatically.
Think of a shuttle in orbit, where there is no air resistance. The shuttle is orbiting the earth at a pretty good clip. When a satellite is released from the shuttle bay, does it suddenly lose that speed, and fall way behind the shuttle? No, it stays with it.
Yeah, but I think the blocks a lot of people have that prevents the shuttle example from being very useful are a) the shuttle is “coasting” in it’s orbit, whilst the car is burning fuel to keep its speed and b) there is air resistance.
As an exercise, would anyone care to figure how far forward the ball travels. Car travelling at 70 MPH car through still air (relative to the ground, of course), standard issue baseball dropped from 2 meters (so you’re in a Chevy Suburban – sue me!).
From a 2 meter height, the ball will stay in the air for 0.639 seconds. Ignoring air resistance, the ball will travel the same distance as the 70 MPH vehicle over this period of time, or about 65.6 feet.
From the perspective of the person in the car, the ball will fall vertically to the ground and then bounce backwards back down the road (friction when the ball hits the ground and all). From the perspective of a stationary observer standing on the side the of the road, the ball will following and arcing path from the time it is dropped until it strikes the ground.
Johnnny LA is correct! There was no “bombs away” switch. The actual switch was the cross hairs. When the two came together, the curcuit was completed and out went the bombs. (Don’t slip)
As far as whether the plane was auto pilot or flown by the bomber. Sorta both. If the bombardier turned his little dial, the plane would turn and correct the coarse automatically. If the bombardier slipped or turned the knobs too much too fast, the plane would turn sharply.
Back on topic:
spritle, let’s not forget that gravity is ALWAYS acting on the ball. When the ball is at rest in our hand, the force of gravity is still acting on it. The ball stays at rest because our hand is applying an equal and opposite force. I know you knew that, but I just want to clear it up for the others 