Kinematics
I have a 1000 kg car that is accelerating at 2 m/s2. How far does it go in 5 seconds?
x=1/2at=25 m
If I push a car with a mass of 200 kg with a force of 250 N and my friends push a bus with a mass of 600 kg with a force of 400 N which vehicle is accelerating faster?
My friends
a=F/m
250/200=1.25 m/s2
600/400= 1.5 m/s2
If a bird is in the air and it's just hovering does it have more potential energy or kinetic energy?
It has more potential energy
If a bicycle and a train are moving at the same speed which one has more momentum? Why?
The train because it has a bigger mass.
f I shoot a cannon perfectly horizontally off a cliff and at the same exact time I drop a ball from the cliff, which will land on the ground first?
They will both hit the ground at the same time
If I drop a ball off a cliff and it takes 4 seconds for it to hit the ground, how tall is the cliff?
h=1/2gt2=5x16=80 m
Will it take more force to open a door by pushing on end or by pushing toward the hinge? How come?
It'll take more force to open it by pushing towards the hinge because the lever arm is shorter
t=FL
As a skier slides down a mountain what happens to his potential energy and kinetic energy?
His potential energy will go down and his kinetic energy will go down.
If the momentum of a car (m=1000 kg) is 20,000 kg*m/s, how fast is the car moving?
p=mv
20,000=1,000v
v=20 m/s
Why do we need friction to move?
It keeps us from sliding around everywhere
If I am travelling at 20 m/s, not accelerating, how far will I travel in 5 s.
xf=xi+vt=0+20(5)=100 m
If something weighs 100 N on a different planet, where the acceleration due to gravity is only 5 m/s2, what is the object's mass?
w=mg
100=5m
m=20 kg
If a frictional force of 3 N acts against a jetski that is moving 30 meters how much work did the friction do against the jetski?
W=Fd
W=3(30)=90 J
If a car (m=1000 kg, v=20 m/s) that is travelling to the right hits a truck (m=2000 kg, v=5 m/s) that is travelling to the left, which direction will the cars move together after collision?
To the right (car has greater momentum)
p=mv
Car: p=1000(20)=20,000
Truck: p=2000(5)=10,000
If the Earth exerts a force on you (gravity), Newton's third law states that you exert a force back on the Earth. Then why doesn't the Earth accelerate towards you when you jump in the air?
The Earth's mass is much greater.
F=ma. Even though the forces are the same, the Earth accelerates much less because its mass is so much greater.
If I start with a velocity of 10 m/s and reach a final velocity of 100 m/s in 9 s, what is my acceleration?
vf=at+vi
100=9t+10
t=10 s
Torques must equal each other.
T=FL
60*10*2=m*10*3
m=40 kg
If a ball (m=100 g) is thrown in the air to a height of 2 m, how much potential energy does it have when it reaches its highest point?
PE=mgh=0.1kg(10)(2)=2 J
A blue air hockey puck that has a mass of 2 kg is at rest. It gets hit by a red air hockey puck that has a mass of1 kg and is moving at a velocity of 5 m/s. If the blue puck is moving at a velocity of 2 m/s now, how fast is the red one going?
It will be going 1 m/s
What part of the wheel is moving faster a part on the outside or a part on the inside?
A part on the outside because it travels a farther distance.
An object is thrown vertically up from the ground with a velocity of 30 m/s. When will it reach its highest point?
vf=vi+at
0=30+(-10)t
t=3 s
If I push on a box with 10 N of force to the right, and my friend pushes on the box with 4 N of force to the left, the box moves to the right with an acceleration of 2 m/s2. What is the mass of the box?
Fnet=ma
10-4=2m
m=3 kg
If a baseball with a mass of .5 kg is 50 meters in the air and is stopped in the air. When it falls back down what is it's speed right before it hits the ground
mgh=1/2mv2
gh=1/2v2
sqrt(10)(50)(2)
31.62
Two comets (both with a mass of 2,000 kg) are moving toward one another. One is moving at 500 m/s and the velocity of the other is unknown. After collision, they have a collective velocity of 200 m/s. What was the initial velocity of the other comet?
pf=mv=4,000(200)=800,000=pi
800,000=MV-mv=2000(500)-2000v
v=100 m/s
How deep do I have to dive to reach a Pb of twice Patm? Density of water is 1000 kg/m3 and Patm is 100,000 Pa.
Pb = Pt + ρgh
200,000 = 100,000 + 1000(10)h
h=10