The amount of heat needed to melt the block of lead is 
Explanation:
The amount of heat needed to melt a solid substance already at its melting point is given by the equation

where
m is the mass of the substance
is the specific latent heat of fusion
In this problem, we have a block of lead already at its melting point,
. Its mass is
m = 200 g = 0.2 kg
and its specific latent heat of fusion is

Therefore, the amount of heat needed for the block to completely melt is

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Answer:
Explanation:
The distance will be the total distannce covered during the journey.
If you move 3 meters East and move 4 meters north, then the distance will be calculated as;
Distance = distnace through East+distance through north
Distance = 3m + 4m
<em>Distance = 7m</em>
Displacement is the distance covered in a specified direction. It is the shortest distance covered by me. This can be gotten using the Pythagoras theorem.
d² = 3²+4²
d² = 9+16
d² = 25
d = √25
d = 5m
<em>Hence the displacement of the object is 5metres</em>
Answer: a scientific theory must be testable and capable of being proven false.
Answer:

Explanation:
As we know that when runner is moving on straight track then the net force on his feet is given as

while when runner is moving on circular track then we have




now percentage change is given as



X2 = 60
/ 2 / 2
x = 30
Plus or minus square root 60