liter of gasoline to kinetic energy, and use all that kinetic
energy to launch a 1 kilogram mass in the air, approximately how
high would it go? assume the gas is high octane fuel containing about 50 million joules of energy per liter
.5 kilometers (500 meters)
5 kilometers (5000 meters)
50 kilometers (50,000 meters)
500 kilometers (500,000 meters)
5000 kilometers (5,000,000 meters
** I chose 5 kilometers
2. Imagine that an astronaught weights 800 Newtons on Earth. How much will she weigh on the surface a planet with Twice the radius of Earth, and four times the mass?
800 Newtons
400 Newtons
100 Newtons
1600 Newtons
** I chose 1600 Newtons
3. Imagine that two football fans try to slide identical ice blocks
down two ramps from the top shelf of the freezer to their beer
coolers. Both ramps are the same height, but one is twice as long
as the other (so that it makes a shallower angle). Since they are
competitive people, they make a race of out it. Which Ice block
will win, and why?
a. The one that slides down the steeper ramp will win because
it has greater kinetic energy at the bottom of the ramp.
b. The one that slides down the shallower ramp will win,
because it will loose less potential energy.
c. they will both reach the ground at the same time since they
both will have the same kinetic energy at the bottom.
d. since both blocks will have the same kineitc energy at the
bottom, the one that travels the shorter, steeper ramp will
win.
** I chose answer a.
4. Two shopping carts, one filled with ten bricks and one filled with twenty bricks are pushed by identical twin shoppers with equal forces over equal distances until they get to the edge of a parking
lot. which of the two carts will have greater kinetic energy at the edge?
a. The cart with 20 bricks
b. Both the same
c. The cart with 10 bricks
** my answer b. both the same
5. Consider molecules of hydrogen gas and heavier molecules of oxygen gas that have the same kinetic energy. The molecules with more speed are:
Oxygen
could be either...there isn't enough information to tell
Hydrogen
Both the same
** my answer is hydrogen
6. Many people think that the force of gravity falls to zero just above the Earth's atmosphere. To refute this, how far away from the Earth's surface would you have to go before the force fell to one fourth is previous value?
About 60 times the radius of the Earth.
About three times the radius of the Earth
About one Earth Radius
About four times the radius of the Earth
** I picked the third answer about one earth radius
7. If the Polar caps melted and flowed towards the equator, the rotation of the Earth would tend to:
Speed up (the day would shorten)
Slow down (the day would lengthen)
Stay the same
It depends on the phase of the moon
** I chose stay the same
8. If you could throw projectile horizontally from a platform so high
that it was just above the Earth's atmosphere, how fast would you
have to throw it to get it orbit the Earth? (note that at that
height, the accleration of gravity is still very close to 9.8
m/s/s).
a bit over 11 km/s
the speed of light.
just over 100 feet/s
a bit under 8 km/s
** I picked the first answer a bit over 11 m/s
9. Two twin brothers, one a kung-fu fighter and the other one a boxer
each throw a punch that strikes their oponents with the same speed.
The kung-fu figher stops his punch in one fourth the time that the
boxer stops his (i.e. their fists come to rest at different times).
Compared with the boxer, the Kung-Fu figher's punch delivers the
greater:
impulse
change in momentum
force
** I picked force as the answer
Thank you.Can someone double check my physics homework please!! Please help!?
1) E = m*g*h. h = E/(m*g) for E J, m = kg, g = 9.8 so h = 50*10^6/9.8 = 5.1*10^6 m = 5,100 km
2) Increased mass = 4X, Increased radius is (1/2)虏x so the result is 4*1/4 = 1. He will weigh the same, 800 N
3) d. The acceleration down the slope is g*sin胃, and the distance down the slope is h/sin胃. The time is t = 鈭歔2*s/a] =鈭歔2*(h/sin胃)/(g*sin胃)] = 鈭歔2*h/g]/sin胃. Lower angle 胃 means more time. Both have the same energy at the end of the ramp, = m*g*h.
4) b. The energy imparted by the force is F*d, and that will be the kinetic energy of the carts. Since F and d are the same, the energy is the same.
5) Hydrogen. The lighter particle needs more speed to have equal energy
6) one earth radius. The total distance is doubled, and gravity reduces by a factor of 4.
7) Slow down. Angular momentum is conserved. With more mass at the equator, more mass is at max distance from the axis of rotation, increasing the moment of inertia, and angular momentum is angular velocity time moment of inertia. If the moment increases, the angular velocity must decrease.
8). The orbital velocity is v = 鈭歔R*g] where R is the orbital radius. The orbital radius is the earth radius + atmosphere depth. If you use 6371 km for earth radius and 16 km for atmosphere depth, you get v = 7.9 km/s
9) force. The change in momentum is the same (assuming the masses are the same). impulse equals momentum change so it is also the same.
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