a 2646lb car is moving on the freeway at 69 mph.
(a) Find the magnitude of its momentum and its kinetic energy in SI units.
(b) At what speed, in m/s, will the car's momentum be half of what it is in part (a).
(c) At what speed, in m/s, will the cats kinetic energy be half of what it is in part (a)
If you are a teacher, which I doubt, you should have failed physics in college. If you are an imposter, stop it.
chyene:
a. change to SI units, monetum=massinKg*velocityinm/s
b. halve the speed to halve the momentum.
c. reduce the speed to speed/sqrt(2)=.707 speed
bobpursley, i am sorry your that way i past it and i am sorry i wrote it wrong
Ms.Black -- do you mean?
"Bobpursley, I am sorry you're that way. I passed it and I am sorry I wrote it wrong."
I am a teacher i am a 2nd grade if has been 19 years since i have done this level physics
You should provide a better English model for your students. Heaven help them if they don't know to capitalize I and that you're means you are. You apparently are not teaching them to begin sentences with capital letters and end them with periods.
I am a math teacher.
For 2nd grade? Please!!
It doesn't really matter what grade or subject you teach, if you can't write better in English than that, you have no business in a classroom.
Amen!
To find the answers to these questions, we can use the formulas for momentum and kinetic energy.
(a) The momentum (p) of an object is given by the product of its mass (m) and velocity (v): p = m * v.
Given that the mass of the car is 2646 lb, we need to convert it to kilograms since we're using SI units. 1 lb is approximately 0.4536 kg. Hence, the mass of the car is approximately 2646 lb * 0.4536 kg/lb = 1198.77 kg.
The velocity of the car is 69 mph, so we need to convert it to m/s. 1 mph is approximately 0.44704 m/s. Hence, the velocity of the car is approximately 69 mph * 0.44704 m/s/mph = 30.84 m/s.
Now we can calculate the magnitude of the momentum:
p = m * v = 1198.77 kg * 30.84 m/s ≈ 36953.22 kg·m/s.
The kinetic energy (K) of an object is given by the formula: K = (1/2) * m * v^2.
Let's calculate the kinetic energy:
K = (1/2) * m * v^2 = (1/2) * 1198.77 kg * (30.84 m/s)^2 ≈ 562,075.27 kg·m^2/s^2 or Joules (J).
(b) To find the speed at which the car's momentum is half, we can set the momentum equal to half its original value and solve for the velocity:
p/2 = m * v'
v' = (p/2) / m.
Substituting the values, we get:
v' = (36953.22 kg·m/s / 2) / 1198.77 kg ≈ 15.42 m/s.
So, the speed at which the car's momentum is half its original value is approximately 15.42 m/s.
(c) To find the speed at which the car's kinetic energy is half, we can set the kinetic energy equal to half its original value and solve for the velocity:
K/2 = (1/2) * m * v'^2.
Rearranging the equation:
v'^2 = (K/2) / (1/2) / m = K / m.
Taking the square root of both sides:
v' = √(K / m).
Substituting the values, we get:
v' = √(562,075.27 kg·m^2/s^2 / 1198.77 kg) ≈ 21.17 m/s.
So, the speed at which the car's kinetic energy is half its original value is approximately 21.17 m/s.
on b), twice the mass means twice the momentum and twice the energy.
a) change 65mph to m/s. To check that, put this in your google search window:
65miles/hr in m/s