Answer:
C.
Explanation:
A person pushing a couch will face resistive force of friction . When resistive force is greater then his force of effort , couch will not move. This force is static friction because the couch is stationary. When the force of effort is increased , magnitude of static friction also increases keeping the couch stationary. The ability of the static friction to increase its magnitude is limited by a maximum value beyond which the couch starts moving. The static friction is then converted into kinetic friction.
In rest of the three cases object is already moving so kinetic friction is in action.
Answer:
Ft
Explanation:
We are given that
Initial velocity=u=0
We have to find the magnitude of p of the momentum of the particle at time t.
Let mass of particle=m
Applied force=F
Acceleration, 
Final velocity , 
Substitute the values

We know that
Momentum, p=mv
Using the formula

B. An image that is larger than the object and is in front of the mirror
Answer:i=300 mA
Explanation:
Given
inductance(L)=40 mH
Resistor(R)=
Voltage(V)=15 V
Time constant(
)=

current 

Current as a function of time is given by

i= 299.95 mA
Answer:

Explanation:
After time "t" the angular position of A is given as

now we know that B start motion after time t1
so its angular position is also same as that of position of A after same time "t"
so we have

now since both positions are same



