Motion in two dimensions and radial acceleration

In summary: He throws them horizontally at a time 6.00 s after Henrietta has passed below the window, and she catches them on the run. With what initial speed must Bruce throw the bagels so Henrietta can catch them just before they hit the ground? Take free fall acceleration to be g = 9.80 m/s^2. Henrietta is located at the window at the time of the throw and catches the bagels just before they hit the ground.
  • #1
pilate
4
0
Hi all! Brand new to these forums. Hopefully I fit in. I'm in my first physics class ever this semester. Physics 1301 Heat and Mechanics.
I'm having a hard time keeping up with everything. I'm looking for some help with a few questions of my homework, because I'm just stuck.

1)The radius of the Earth's orbit around the sun (assumed to be circular) is 1.50 \times 10^8 km, and the Earth travels around this orbit in 365 days.a)What is the magnitude of the orbital velocity of the Earth in m/s? b) What is the radial acceleration of the Earth toward the sun?

a) I don't know where to start! I've read this section of the book word for word and I can't find a thing related to |v|.
b)All the equations I have require me to know velocity. I should be able to do this alright with v^2/radius

2)Henrietta is going off to her physics class, jogging down the sidewalk at a speed of 3.75 m/s. Her husband Bruce suddenly realizes that she left in such a hurry that she forgot her lunch of bagels, so he runs to the window of their apartment, which is a height 35.9 m above the street level and directly above the sidewalk, to throw them to her. Bruce throws them horizontally at a time 6.00 s after Henrietta has passed below the window, and she catches them on the run. You can ignore air resistance. a)With what initial speed must Bruce throw the bagels so Henrietta can catch them just before they hit the ground? Take free fall acceleration to be g = 9.80 m/s^2. b) Where is Henrietta when she catches the bagels?

a)The only thing I could think to do was y-y(initial)= v(initial)t+1/2*g*t^2 and solve for v(initial). t=6seconds g=9.8m/s^2 y-y(initial)=35.9m
b)I'm guessing this would be the x=x(initial)=v(initial)t+1/2at^2

Thanks in advance for your help.
 
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  • #2
speed = distance / time
 
  • #3
andrewchang said:
speed = distance / time
I tried that. The homework is submitted online so I can enter in an answer and find out right away if it's correct. That formula wasn't correct.
 
  • #4
are you sure about the right units and equations?
show me what you did
 
  • #5
part 1 of problem one is definitely speed=distance/time, but the radius isn't the total distance travelled. try to figure out a way to find the total distance traveled in 1 whole revolution round the sun.

for part 2, you can use the equations of pseudo forces for circular motion.
 
  • #6
andrewchang said:
are you sure about the right units and equations?
show me what you did

Code:
1.50X10^8 km    1000 m   1 day      4756 m
--------------  -------  ------   =  --------
365 days         1 km     86,400 s   seconds
which comes up as wrong.
@aalmighty: I don't understand.
 
  • #7
do you know the equation for the circumference of a circle? what path does the planet travel?
 
  • #8
andrewchang said:
do you know the equation for the circumference of a circle? what path does the planet travel?
I just had an "Ah ha!"
Thank you.

Now any help for problem 2?
 
Last edited:

What is the difference between motion in one dimension and motion in two dimensions?

Motion in one dimension refers to movement along a single axis, typically represented by a straight line. This means that the object is only moving forward or backward. On the other hand, motion in two dimensions involves movement in both the x and y directions, creating a curved or diagonal path.

What is radial acceleration and how is it different from tangential acceleration?

Radial acceleration is the acceleration towards or away from the center of a circular path. It is perpendicular to the tangential acceleration, which is the acceleration along the tangent of the circular path. Essentially, radial acceleration determines how fast an object is changing its direction while tangential acceleration determines how fast it is changing its speed.

How is radial acceleration related to centripetal force?

Radial acceleration is directly proportional to centripetal force, which is the force that keeps an object moving in a circular path. The greater the radial acceleration, the greater the centripetal force needed to maintain the circular motion. In other words, the force pulling the object towards the center of the circle must be strong enough to counteract the object's tendency to move in a straight line.

Can an object experience both radial and tangential acceleration at the same time?

Yes, an object can experience both types of acceleration simultaneously. This is common in circular motion, where the object is constantly changing direction and speed. The combination of radial and tangential acceleration determines the overall acceleration of the object at any given point in its path.

How do you calculate the magnitude and direction of radial acceleration?

The magnitude of radial acceleration can be calculated using the formula ar = v2/r, where v is the speed of the object and r is the radius of the circular path. The direction of radial acceleration is always towards the center of the circle. This means that if an object is moving clockwise, the direction of radial acceleration will be towards the center of the circle in a counterclockwise direction, and vice versa.

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