Answer:
From the second law of motion:
F = ma
we are given that the force applied on the block is 20N and the block accelerates at an acceleration of 4 m/s/s
So, F= 20N and a = 4 m/s/s
Replacing the variables in the equation:
20 = 4* m
m = 20 / 4
m = 5 kg
Answer:
1. a 
b 
c 
2. 
Explanation:
a). The work done by the tension is:




b). The work done potential of gravity




c). The work done by the normal force



2. The increase in thermal energy is:





B is the answer that I know of.
Answer:
The length of the stick is 0.28 m.
The time the stick take to move is 0.97 ns.
Explanation:
Given that,
Relative speed of stick v= 0.96 c
Speed of light 
Proper length of stick = 1 m
We need to calculate the length of the stick
Using formula of length

Put the value into the formula



We need to calculate the time the stick take to move
Using formula of time

Put the value into the formula



Hence, The length of the stick is 0.28 m.
The time the stick take to move is 0.97 ns.
The circuit change when the wire is added will see a short circuit occur and makes bulbs 1 and 2 turn off but keeps bulbs 3 and 4 lit. Option D. This is further explained below.
<h3>
How does the circuit change when the wire is added?</h3>
Generally, Electronic circuits consist of a series of interconnected parts that form a closed loop through which electricity may flow.
In conclusion, If two wires are linked together, a short circuit will develop, cutting power to bulbs 1 and 2. But there is no impact on bulbs 3 and 4. There is no problem with bulbs 3 and 4.
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