What are the given choices?
Answer:
25.7 N
44.8 N
Explanation:
Draw a free body diagram of the block. There are three forces: weight force mg pulling down, buoyancy force ρVg pushing up, and normal force N pushing up.
Sum of forces in the y direction:
∑F = ma
N + ρVg − mg = 0
N = mg − ρVg
N = (3.5 kg) (9.8 m/s²) − (1000 kg/m³) (3.5 kg / 4000 kg/m³) (9.8 m/s²)
N = 25.7 N
The water pushes up on the block with a buoyancy force of ρVg. According to Newton's third law, the block pushes back down on the water with an equal force of ρVg.
The other forces are weight force Mg pulling down, and normal force N pushing up.
Sum of forces in the y-direction:
∑F = ma
N − ρVg − Mg = 0
N = Mg + ρVg
N = (1.4 kg + 2.3 kg) (9.8 m/s²) + (1000 kg/m³) (3.5 kg / 4000 kg/m³) (9.8 m/s²)
N = 44.8 N
Answer: the number protons stayed the same.
Explanation: an isotope has equal number of protons but different number of neutrons resulting in different atomic mass but the same chemical properties.
The car accelerates with magnitude <em>a</em> such that
31.3 m/s = 25.6 m/s + <em>a</em> (5.4 s)
→ <em>a</em> = (31.3 m/s - 25.6 m/s) / (5.4 s) ≈ 1.056 m/s²
Then the applied force has a magnitude <em>F</em> of
<em>F</em> = (1430 kg) <em>a</em> ≈ 1500 N