A:True because Lithium is the lighest solid and metal and the third lightest element.
Answer with explanation:
We are given that
Mass of ball,
75 g=
1 kg=1000 g
Height,

Horizontal velocity,
Mass of plate
a.Initial velocity of plate,
Velocity before impact=
Where 
Velocity after impact,
According to law of conservation of momentum

Substitute the values



Velocity of plate=1.69 m/s
b.Initial energy=
Final energy=
Final energy=
Energy lost due to compact=Initial energy-final energy=1.326-1.162=0.164 J
Answer:
20 hertz of frequency produced.
Explanation:

Here we will find frequency and period should be in second, here given: 0.05 seconds
using the formula:


Answer:
A(many people think that no energy or matter exists outside the universe)
Explanation: