Answer:
M.A = load/ effort
1200N/400N
= 3
velocity ratio= radius of wheel/radius of Axle
40cm/10cm
=4
efficiency= 3/4*100
75%
Answer:
The final acceleration becomes (1/3) of the initial acceleration.
Explanation:
The second law of motion gives the relationship between the net force, mass and the acceleration of an object. It is given by :

m = mass
a = acceleration
According to given condition, if the mass of a sliding block is tripled while a constant net force is applied. We need to find how much does the acceleration decrease.

Let a' is the final acceleration,

m' = 3m



So, the final acceleration becomes (1/3) of the initial acceleration. Hence, this is the required solution.
D. mechanical energy is transformed into sound energy.
Answer:
7.50 cm
Explanation:
The formula
1/v + 1/u = 1/f
Is used.
where.
u is the object distance.
v is the image distance.
f is the focal length of the lens.
1/v + 1/15 = 1/5
1/v = 1/5 - 1/15
1/v = (3-1)/15
1/v = 2/15
2v = 15
V = 15/2
V = 7.5 cm
For focal length, f in lens is always taken as negative for concave and positive for convex. ... And for image distance, V in lens it is taken as positive in Convex lens since image is formed on +X side. It is taken as negative in Concave lens since image is formed in -X side of the Cartesian.