The mass of the ball is inversely proportional to acceleration of a ball.
<h3>What is friction?</h3>
This question is incomplete but I will try to help you the much I can. Friction is the force that opposes motion. Friction depends on the nature of the surfaces in contact.
When the mass of the ball is large, the acceleration of the ball decreases since mass is inversely proportional to acceleration of a body.
Learn more about acceleration: brainly.com/question/2437624
The final velocity of the block A will be 2.5 m/sec. The principal of the momentum conversation is used in the given problem.
<h3>What is the law of conservation of momentum?</h3>
According to the law of conservation of momentum, the momentum of the body before the collision is always equal to the momentum of the body after the collision.
In a given concern, mass m₁ is M, mass m₂ is 3M. Initial speed for the mass m₁ and m₂ will be u₁=5 and u₂=0 m/s respectively,
According to the law of conservation of momentum
Momentum before collision =Momentum after collision
m₁u₁+m₂u₂=(m₁+m₂)v
M×5+3M×0=[M+3M]v
The final velocity is found as;
V=51.25 m/s
The velocity of block A is found as;

Hence, the final velocity of the block A will be 2.5 m/sec.
To learn more about the law of conservation of momentum, refer;
brainly.com/question/1113396
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Here is your answer
b) 
REASON :
We know that
Velocity= Frequency× Wavelength
So,
Frequency= Velocity/wavelength
Here,
V= 3× 10^8 m/s
Wavelength= 2×10^-3 m
Hence,
Frequency= 3×10^8/2×10^-3
= 3/2 × 10^11
= 1.5× 10^11 Hz
HOPE IT IS USEFUL
<span>The combined
gas law has no official founder; it is simply the incorporation of the three
laws that was discovered. The combined gas law is a gas law that combines
Gay-Lussac’s Law, Boyle’s Law and Charle’s Law.
Boyle’s law states that pressure is inversely proportional with volume
at constant temperature. Charle’s law states that volume is directly
proportional with temperature at constant pressure. And Gay-Lussac’s law shows
that pressure is directly proportional with temperature at constant volume. The
combination of these laws known now as combined gas law gives the ratio between
the product of pressure-volume and the temperature of the system is constant.
Which gives PV/T=k(constant). When comparing a substance under different
conditions, the combined gas law becomes P1V1/T1 = P2V2/T2.</span>