Answer:
Second choice
Explanation:
I suppose ME is the same as POTENTIAL energy
ME = mgh = 70 * 10 * 12 = 8400j
Half way down, 4200 j is converted to Kinetic Energy
1/2 m v^2 = 4200
1/2 (70) v^2 = 4200 v = 10.95 m/s
Just before impact ALL of the 8400 j is now KE
1/2 (70)v^2 = 8400 v = 15.49 m/s
Explanation:
Draw a free body diagram of the toolbox. There are two forces:
Weight force mg pulling down,
and applied force F pulling up.
Sum of forces in the y direction:
∑F = ma
F − mg = ma
45 N − 15 N = (3 kg) a
a = 10 m/s²
The answer should be B. It's possible the answer key has a mistake.
Answer:
9.6 km/h
Explanation:
20 minutes=1/3 minute.
The speed of the bicycle: 3.2:1/3=9.6 km/h.
Answer: 9.6 km/h