Answer:
Option A is the correct answer.
Explanation:
Here momentum is conserved.
That is 
Substituting values

Speed of block A after collision = 10 m/s
Option A is the correct answer.
<span>Density can be calculated and found by dividing the sample's mass by its volume. D=m/v</span>
Answer:
6.67 ohm
Explanation:
From the question given above, the following data were obtained:
Resistor 1 (R₁) =20 ohm
Resistor 2 (R₂) = 20 ohm
Resistor 3 (R₃) = 20 ohm
Equivalent Resistance (R) =?
Since the resistors are arranged in parallel connection, the equivalent resistance can be obtained as follow:
1/R = 1/R₁ + 1/R₂ + 1/R₃
1/R = 1/20 + 1/20 + 1/20
1/R = (1 + 1 + 1) / 20
1/R = 3/20
Invert
R = 20/3
R = 6.67 ohm
Therefore, the equivalent resistance is 6.67 ohm.