Posted by Ariel on Monday, July 12, 2010 at 2:31pm.
Since I've been waiting to get my answers checked for my submission #2, I moved on to my submission #3 and I need some questions checked for my submission #3 please.
1.)If a blue car drives 10km/h across the deck of an ocean liner that is traveling at 90km/h, what is the blue car's speed relative to the surface of the water when it drives toward the front of the ocean liner?
a)10 km/h
b)80 km/h
c)90 km/h
=d)100 km/h
2.)A motorboat travels at a speed of 40 km/h relative to the surface of the water. If it travels upstream against a current of 12 km/h what is the boats speed relative to the shore?
a)3.3 km/h
=b)28 km/h
c)40 km/h
d)52 km/h
3.)An airplane flies north at a speed of 150 km/h relative to the air through which it flies. If there is a tail wind of 50 km/h, what is the plane's velocity relative to the ground?
a)3 km/h north
=b)100 km/h north
c)150 km/h north
d)200 km/h north
4.)A plane flying 100km/h due north encounters a crosswind of 100km/h "from the east" (i.e. blowing westward). What then, is the plane's velocity relative to the ground?
a)141.4 km/h northeast
=b)141.4 km/h northwest
c)100 km/h northeast
d)100 km/h northwest
5.)A bullet is shot from a rifle aimed horizontally at the same time a bullet is dropped from the same height as the gun's barrel. Which bullet hits the ground first?
a)The fired bullet
=b)The dropped bullet
c)Both bullets the ground at the same time
6.)A car drives off a vertical cliff that is 122.5m tall. If the car lands 100m from the base of the cliff what was the cars speed as it drove off the cliff.
a)20m/s
=b)22m/s
c)24m/s
d)26m/s
(#6 I just really guessed because I don't know what to do so I just 122.5100=22.5 so I just stuck with that.)

Physics Check  Quidditch, Monday, July 12, 2010 at 5:30pm
#1 correct
#2 correct
#3 wrong
#4 correct
#5 wrong

#6
find t in seconds:
122.5m = (0.5)(g)(t^2)
122.5m = (0.5)(9.8m/s^2)t^2
reducing...
25s^2 = t^2
t = +5 seconds and t = 5 seconds
Disregard the negative time.
That is how long it took to fall 122.5m.
So, if the car traveled horizontally 100m in 5 seconds, speed is 100m/5s = 20m/s which is the answer a.

Physics Check  Quidditch, Monday, July 12, 2010 at 5:42pm
A more complete explanation...
The car is traveling horizontally at a constant speed. When it drives off the cliff, it keeps going at the same speed (disregarding friction) until it is stopped by hitting the ground. A forumla for (d) distance traveled with constant acceleration, no initial vertical velocity is:
d = (1/2)(a)(t^2)
where a is the acceleration and t is the time. The acceleration due to gravity is about 9.8m/s^2.
d is given as 122.5m.
Once the falling time is found that can be plugged into the formula for speed.
In this case it took 5 seconds to fall, and the car traveled 100m in that time.

Physics Check  Damon, Monday, July 12, 2010 at 5:46pm
In number 5 both bullets fall at the same rate. The horizontal problem has nothing to do with the vertical problem except that the time in the air is the same.

Physics Check  Ariel, Tuesday, July 13, 2010 at 1:01pm
Thanks:)

Physics Check  ANA, Wednesday, October 6, 2010 at 1:50pm
A motorboat travels at a speed of 40 km/h relative to the surface of the water. If it travels upstream against a current of 12 km/h what is the boats speed relative to the shore?

Physics Check  ANA, Wednesday, October 6, 2010 at 1:54pm
An airplane flies north at a speed of 150 km/h relative to the air through which it flies. If there is a tail wind of 50 km/h, what is the plane's velocity relative to the ground?

Physics Check  iz, Tuesday, August 16, 2011 at 12:24pm
.)An airplane flies north at a speed of 150 km/h relative to the air through which it flies. If there is a tail wind of 50 km/h, what is the plane's velocity relative to the ground?
200 km/h north

Physics Check  iz, Tuesday, August 23, 2011 at 12:44pm
.)An airplane flies north at a speed of 150 km/h relative to the air through which it flies. If there is a tail wind of 50 km/h, what is the plane's velocity relative to the ground?
150 km/h

Physics Check  your face, Thursday, January 10, 2013 at 5:56pm
who really cares?
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