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# Motion Help! :( watch

1. A ball rolls with a speed of 2 m/s across a level table that is 1.0 m above the floor. Upon reaching the edge of the table, it follows a parabolic path to the floor. How far along the floor is the landing spot from the table?

A rescue pilot drops a survival kit while her plane is flying at an altitude of 2000 m with a forward velocity of 100 m/s. If air friction is disregarded, how far in advance of the starving explorer’s drop zone should she release the package?

I dont really know what to do and i dont completely understand the horizontal/vertical component... In questions like these should we assume the angle is 90 degrees ?
2. bump
3. (Original post by princejan7)
A ball rolls with a speed of 2 m/s across a level table that is 1.0 m above the floor. Upon reaching the edge of the table, it follows a parabolic path to the floor. How far along the floor is the landing spot from the table?

A rescue pilot drops a survival kit while her plane is flying at an altitude of 2000 m with a forward velocity of 100 m/s. If air friction is disregarded, how far in advance of the starving explorer’s drop zone should she release the package?

I dont really know what to do and i dont completely understand the horizontal/vertical component... In questions like these should we assume the angle is 90 degrees ?
Horizontal and vertical components are always perpendicular to each other, so that's always assumed. You also assume in these questions that there is no air resistance or friction on the moving objects.

For these questions you just have to use suvat equations, which are v = u + at, s = ut + ½at² and v² = u² + 2as. You'll have to deduce the values of s, u, v, a and t from the questions and use them to work out other unknown information. If the object is falling, then you always assume that g = 9.81 m/s² unless told otherwise. You should always choose an equation with only 1 unknown.

For the first problem, you have to use the known information to work a value out the value of t for one component, and then use that value along with the other information to work out the distance for the second component.

For the second problem, you basically do the same.
4. (Original post by OL1V3R)
Horizontal and vertical components are always perpendicular to each other, so that's always assumed. You also assume in these questions that there is no air resistance or friction on the moving objects.

For these questions you just have to use suvat equations, which are v = u + at, s = ut + ½at² and v² = u² + 2as. You'll have to deduce the values of s, u, v, a and t from the questions and use them to work out other unknown information. If the object is falling, then you always assume that g = 9.81 m/s² unless told otherwise. You should always choose an equation with only 1 unknown.

For the first problem, you have to use the known information to work a value out the value of t for one component, and then use that value along with the other information to work out the distance for the second component.

For the second problem, you basically do the same.
thanks! But for eg. in the first question, if i take 2 * cos90 for the horizontal component, i end up getting zero for the horizontal velocity and the range...
5. (Original post by princejan7)
A ball rolls with a speed of 2 m/s across a level table that is 1.0 m above the floor. Upon reaching the edge of the table, it follows a parabolic path to the floor. How far along the floor is the landing spot from the table?

?
Take the vertical motion first. This can be considered independently of the horizontal.
How long does it take the object to fall the 1m from the tabletop to the floor.
Initially it has no downwards motion so
u=0
a=9.81m/s/s
s=1m
use an equation to find t. [you should know these so-called "suvat" equations]
When you have calculated the time, t, use this to find out how far in the horizontal direction the object moved in this time.
The object had a horizontal velocity of 2m/s along the table. It keeps this horizontal velocity while it falls. So just use distance = velocity x time.

The second question uses the same idea.
6. (Original post by Stonebridge)
Take the vertical motion first. This can be considered independently of the horizontal.
How long does it take the object to fall the 1m from the tabletop to the floor.
Initially it has no downwards motion so
u=0
a=9.81m/s/s
s=1m
use an equation to find t. [you should know these so-called "suvat" equations]
When you have calculated the time, t, use this to find out how far in the horizontal direction the object moved in this time.
The object had a horizontal velocity of 2m/s along the table. It keeps this horizontal velocity while it falls. So just use distance = velocity x time.

The second question uses the same idea.
when calculating the horizontal distance, my horizontal component of velocity works out to 0 ( 2*cos90 ) which leads to a horizontal displacement 0 ( 0.45 * 2*cos90 ) = 0
7. (Original post by princejan7)
when calculating the horizontal distance, my horizontal component of velocity works out to 0 ( 2*cos90 ) which leads to a horizontal displacement 0 ( 0.45 * 2*cos90 ) = 0
Don't use cos and sin to work out the horizontal and vertical velocities, unless the moving object is at an angle in between the two components.

Consider the components separately:

Horizontal

s = ?
u = 2 m/s
a = 0 m/s²
v = not relevant
t = ?

Vertical

s = 1.0 m
u = 0 m/s
a = -9.81 m/s² (remember it's negative, since the acceleration is downwards)
v = not relevant
t = ?

The vertical motion has only one relevant unknown variable so take that first. Use an equation not involving v but involves t, to work out t. Then plug this value into another suvat equation as applied to the horizontal component, to work out the horizontal distance.
8. (Original post by OL1V3R)
Don't use cos and sin to work out the horizontal and vertical velocities, unless the moving object is at an angle in between the two components.

Consider the components separately:

Horizontal

s = ?
u = 2 m/s
a = 0 m/s²
v = not relevant
t = ?

Vertical

s = 1.0 m
u = 0 m/s
a = -9.81 m/s² (remember it's negative, since the acceleration is downwards)
v = not relevant
t = ?

The vertical motion has only one relevant unknown variable so take that first. Use an equation not involving v but involves t, to work out t. Then plug this value into another suvat equation as applied to the horizontal component, to work out the horizontal distance.
In the first question, why isnt the ball at an angle between the two components as it falls off the table?

Sorry for the questions
9. The ball starts off moving purely in a horizontal direction and has no "angle" (other than 0) to the table.
As it falls the angle does increase, but this is because the original horizontal motion is now being combined with more and more vertical component.
The point is, the horizontal motion is independent of the vertical, so you can treat it as though the object moves at a constant 2m/s horizontally until it hits the floor.
The vertical part is taken care of by considering the vertical motion separately, and calculating how long it takes to fall vertically 1m, as I explained in my 1st post.
10. (Original post by OL1V3R)
Don't use cos and sin to work out the horizontal and vertical velocities, unless the moving object is at an angle in between the two components.

Consider the components separately:

Horizontal

s = ?
u = 2 m/s
a = 0 m/s²
v = not relevant
t = ?

Vertical

s = 1.0 m
u = 0 m/s
a = -9.81 m/s² (remember it's negative, since the acceleration is downwards)
v = not relevant
t = ?

The vertical motion has only one relevant unknown variable so take that first. Use an equation not involving v but involves t, to work out t. Then plug this value into another suvat equation as applied to the horizontal component, to work out the horizontal distance.
You don't need suvat for the horizontal component. Just s=vt where v is the horizontal component and s the horizontal displacement.
11. (Original post by OL1V3R)
Horizontal and vertical components are always perpendicular to each other, so that's always assumed. You also assume in these questions that there is no air resistance or friction on the moving objects.

For these questions you just have to use suvat equations, which are v = u + at, s = ut + ½at² and v² = u² + 2as. You'll have to deduce the values of s, u, v, a and t from the questions and use them to work out other unknown information. If the object is falling, then you always assume that g = 9.81 m/s² unless told otherwise. You should always choose an equation with only 1 unknown.

For the first problem, you have to use the known information to work a value out the value of t for one component, and then use that value along with the other information to work out the distance for the second component.

For the second problem, you basically do the same.
you have stellar grades...you would have made it easy into medical school... LOL...we need smart people like you in medicine..LOL ...Keep up the good work.
12. (Original post by int_applicant)
you have stellar grades...you would have made it easy into medical school... LOL...we need smart people like you in medicine..LOL ...Keep up the good work.
Hehe, thanks!

I've always been more of a mathematician, I wasn't really into Biology that much so I didn't want to go to medical school. I was more a Physics/Chemistry person myself!

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