Momentum
Is momentum a vector or a scalar?
A 100. kg man is running at 5.6 m/s. What is his momentum?
560 kg*m/s
Which has greater linear speed, a horse near the outside rail of a merry-go-round or a horse near the inside rail?
the outside horse
How is θ, ω, α pronounced and what are the quantities they represent?
θ, theta, angular displacement
ω, omega, angular velocity
α, alpha, angular acceleration
What is electricity?
flow of electrons
The units for momentum.
kg*m/s
or
N*s
An object, initially travelling at 5.0 m/s, experiences a change in momentum of 25 Kg m/s. What is the impulse on the object?
Impulse is the same as change in momentum. It experiences an impulse of 25 Ns.
What is the direction of the force that acts on clothes in the spin cycle of a washing machine? outward, inward, up, down?
inward. Also called centripetal force which means "center-seeking."
What force is responsible for the centripetal force for a moon?
gravitational force
A 7.87-nC charge is located 1.68 m from a 4.62-nC point charge. Find the electrostatic force that one charge exerts on the other, including direction.
1.16 ✕ 10−7 N away from the other charge
This is conserved when two objects collide
momentum?
A .50 Kg object is traveling at 4.0 m/s right. A force acts on the mass and causes it to travel at 3.0 m/s left. The force acted for .50 seconds. What is the force felt by the mass?
-7.0N OR 7.0N (L)
You sit at the outer rim of a Ferris wheel that rotates at 2 revolutions per minute (RPM). What would your rotational speed be if you were instead clinging to a position halfway from the center to the outer rim?
2 RPM or 2
If you whirl a tin can on the end of a string and the string suddenly breaks, the can will _______________. Name the law of physics that describes this action.
The can will fly off, tangent to its circular path. The law of inertia or Newton's first law.
An electric heater with a resistance of 23.6 Ω carries a current of 14.0 A. What is the operating voltage?
330.V
In an elastic collision this is what happens (conceptually+mathematically).
KE is conserved
so
v1i+v1f=v2i+v2f
The final velocity after car one of 2,200 kg moving at 30. m/s collides with another 2,200 kg car at rest if they collide, lock, and move forward together
15 m/s
A CD rotates from rest up to an angular speed of 31.4 rad/s in a time of 0.5 s. Through what angle does the disc turn while coming up to speed?
Δθ = 7.85 rad
Find the force of gravity between you and the earth at an altitude of 3.12*106m. Assume you have a mass of 60.0 kg. The earth’s mass is 5.98*1024 kg and its mean radius is 6.38*106 m.
265N
What is the cause of voltage? Also explain how voltage causes current.
Voltage is caused by a separation of charges, which causes an electric field. The electric field that causes voltage pushes electrons in one direction, which is current.
Two eggs of the same mass are dropped from the same height. One egg is caught in a bed of cotton. The other eggs is allowed to hit the ground. Which egg is more likely to break and why (reference the impulse-momentum theorem)
The egg that hits the ground. The change in momentum of the eggs are the same. The time of impact is much shorter for the egg that hits the ground and so the average force is much higher.
A 2.0 Kg mass is moving at 10. m/s to the right. It collides with a 4.0 Kg mass that is moving at 8.0 m/s to the right. Both objects are on a frictionless surface. After the collision the 2.0 Kg object moves with a velocity of 9.0 m/s to the right. What is the velocity of the 4.0 Kg mass after the collision?
8.5 m/s (R)
A 1.5kg ball connected to a string is on earth. If it is swung in a circle vertically with a speed of 5.00m/s, what is the tension on the string when the ball passes its maximum height?
22.8N
A satellite orbits the Earth with a tangential velocity of 6000.m/s. What is its altitude?
G=6.67∗10^(-11) N∙m^2/kg^2
mEarth=5.972∗10^24 kg
rEarth=6.371∗10^6 m
4690km
A current of 78.5 mA exists in a metal wire. How many electrons flow past a given cross section of the wire in 1.00s?
4.91*1017electrons
You want to close an open door by throwing either a 400-g lump of clay or a 400-g rubber ball toward it. You can throw either object with the same speed, but they are different in that the rubber ball bounces off the door while the clay just sticks to the door. Which projectile will apply the larger impulse to the door and be more likely to close it? Why will that object have a larger impulse?
The bouncy ball. It not only loses all of its initial momentum it gains momentum in the opposite direction. This results in a larger momentum change and so a larger impulse.
The final velocity of object B with a mass of 2.0kg going 4.0 m/s left (negative) when object A weighs 10kg going 2.0 m/s right (positive)
6.0 m/s (R)
A race car accelerates uniformly from a speed of 40.0 m/s to a a speed of 60.0 m/s in 2.50 s while traveling counterclockwise around a circular track of radius 400. m. When the car reaches a speed of 60.0 m/s, find the total acceleration.
a = 12.0 m/s2
A satellite’s orbital period around the earth is the same as the earth’s period of rotation of 24.0h. What is the altitude of the satellite?
3590km
A small object of mass 3.72 g and charge −18.6 𝜇C is suspended motionless above the ground when immersed in a uniform electric field perpendicular to the ground. What are the magnitude and direction of the electric field?
1960 N/C downward