Pushing a Block On a Block – Qualitative A heavy block, labeled \"A\", is sittin
ID: 1784745 • Letter: P
Question
Pushing a Block On a Block – Qualitative
A heavy block, labeled "A", is sitting on a table. On top of that block is a lighter block, labeled "B" as shown in the figure below.
For the first parts of this problem you are asked to identify the direction of forces in this system under various circumstances. The labels in the subscripts indicate: A = block A, B = block B, F = finger, T = table. Specify the direction in your answers using the following notation.
R means points to the right.
L means points to the left.
U means point up.
D means points down.
0 indicates there is no such force at the instant specified.
(a)
You start pushing on block A as shown, but it is too heavy and does not move. While you are pushing on block A but while it is not moving, specify the direction of the following normal (N) and frictional (f) forces between the various objects indicated.
(i)
NA B
---Select--- R L U D 0
(ii)
fT A
---Select--- R L U D 0
(iii)
fA B
---Select--- R L U D 0
(iv)
NF A
---Select--- R L U D 0
(v)
fB A
---Select--- R L U D 0
(vi)
NB A
---Select--- R L U D 0
(b)
Now you push a little harder and the block begins to move. Block B moves with it without slipping. While the blocks are speeding up specify the direction of the following forces between the various objects indicated.
(i)
NA B
---Select--- R L U D 0
(ii)
fT A
---Select--- R L U D 0
(iii)
fA B
---Select--- R L U D 0
(iv)
NF A
---Select--- R L U D 0
(v)
fB A
---Select--- R L U D 0
(vi)
NB A
---Select--- R L U D 0
(c)
Now you push so that the blocks move at a constant velocity. Block B moves with A without slipping. While the blocks are moving at a constant speed specify the direction of the following forces between the various objects indicated.
(i)
NA B
---Select--- R L U D 0
(ii)
fT A
---Select--- R L U D 0
(iii)
fA B
---Select--- R L U D 0
(iv)
NF A
---Select--- R L U D 0
(v)
fB A
---Select--- R L U D 0
(vi)
NB A
---Select--- R L U D 0
Explanation / Answer
A)
i> NA-> B - U
ii> fT-> A - L
iii> fA-> B -> R
iv> NF->A -> R
v> fB->A -> L
vi> NB -> A -> D
B.>
i> NA->B -> U
ii> ft->A -> L
iii? fA->B-> R
iv> Nf->A -> R
v> fB->A -> L
vi> NB->A -> D
C.>
i> NA->B -> U
ii> ft->A -> L
iii? fA->B-> R
iv> Nf->A -> R
v> fB->A -> L
vi> NB->A -> D
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