Answer:
The frictional force
6.446 N
The acceleration of the block a = 6.04 
Explanation:
Mass of the block = 3.9 kg
°
= 0.22
(a). The frictional force is given by


3.9 × 9.81 × 
29.3 N
Therefore the frictional force
0.22 × 29.3
6.446 N
(b). Block acceleration is given by

F = 30 N
= 6.446 N
= 30 - 6.446
= 23.554 N
The net force acting on the block is given by

23.554 = 3.9 × a
a = 6.04 
This is the acceleration of the block.
Answer: y = 2.4×10^-6m or y= 2.4μm
Explanation: The formulae for the distance between the central bright fringe to any other fringe in pattern is given as
y = R×mλ/d
Where y = distance between nth fringe and Central bright spot fringe.
m = position of fringe = 4
λ = wavelength of light= 600nm = 600×10^-9 m
d = distance between slits = 1.50×10^-5m
R = distance between slit and screen = 2m
y = 2 × 4 × 600×10^-9/2
y = 4800×10^-9/2
y = 2400 × 10^-9
y = 2.4×10^-6m or y= 2.4μm
If the resistor is in series with the rest of the circuit then a is the correct answer. The voltage across the resistor in series with another resistor is

where R is the big resistor and r is the small one and V is the total voltage drop across both. This is called a voltage divider
The mechanical advantage is the factor by which
the machine multiplies the input force.
If the MA is 3 and the input force is 630N, then
the output force is
(3) x (630N) = 1,890N