Answer:
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Explanation:
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact.
The coefficient of friction (fr) is a number that is the ratio of the resistive force of friction (Fr) divided by the normal or perpendicular force (N) pushing the objects together. It is represented by the equation: fr = Fr/N.
Answer:
The velocity of the truck after this elastic collision is 15.7 m/s
Explanation:
It is given that,
Mass of the car, 
Mass of the truck, 
Initial velocity of the car,
Initial velocity of the truck, u₂ = 0
After the collision the velocity of the car is, v₁ = -11 m/s
Let v₂ is the velocity of the truck after this elastic collision. Using the conservation of momentum as :

So, the velocity of the truck after this elastic collision is 15.7 m/s. Hence, the correct option is (c).
Answer:
Decibel Meter
A decibel meter is a measuring instrument used to assess noise or sound levels by measuring sound pressure. Often referred to as a sound pressure level (SPL) meter, decibel (dB) meter, noise meter or noise dosimeter, a sound level meter uses a microphone to capture sound.
1 . W=mass times acceleration due to gravity
60kg times 9.8m/s2
= 588N
2. W=mg
1176N=m times 9.8
m=120kg
3. 1 hour=3600s
24 hours=?
24 times 3600
= 86400 seconds
4. 1000g=1kg
25000g=?
25000 times 1 divide by 1000
=25kg
5. 1000000mg=1kg
123000000=?
123000000 times 1 divide by 1000000
=123 kg