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Answer:
B.The force of friction between the block and surface will decrease.
Explanation:
The force of friction is given by
where is the coefficient of friction and
is the normal force.
When the student pulls on the block with force at an angle
, the normal force on the block becomes
and hence the frictional force becomes
.
Now, as we increase ,
increases which as a result decreases the normal force
, which also means the frictional force decreases; Hence choice B stands true.
<em>P.S: Choice D is tempting but incorrect since the weight </em><em> is independent of the external forces on the block. </em>
Answer:
a)
b)
Explanation:
Given:
mass of the lighter block,
velocity of the lighter block,
mass of the heavier block,
velocity of the heavier block,
a)
Using conservation of linear momentum:
where:
final velocity of the lighter block
final velocity of the heavier block
........................(1)
Since kinetic energy is conserved in elastic collision:
divide the above equation by eq. (1)
.............................(2)
now we substitute the value of v from eq. (2) in eq. (1)
(negative sign denotes that the direction is towards left)
b)
now we substitute the value of v' from eq. (2) in eq. (1)