Average speed=total distance traveled/time. Total distance=the sum of the two short distances=79*2+77*3=389 km. Total time used to travel is 2+3=5 hr. Average speed is 389/5=77.8 km/hr.
Hello!

Use the equation:

Where:
m = mass of the object (kg)
g = acceleration due to gravity (≈9.8 m/s)
h = height above ground (m)
Plug the given values into the equation:
PE = 7500 · 9.8 · 100
PE = 7,350,000 Joules.
Answer:
Incomplete question: The masses of the blocks m₂ = 1.5 kg and m₃ = 2 kg
Explanation:
Given data:
L₁ = length = 0.85 m
L₂ = 0.25 m
L₃ = 0.5 m
m₂ = 1.5 kg
m₃ = 2 kg
Question: Find the unknown mass of the block 1 needed to balance the bar, m₁ = ?
The torque is zero (intermediate point of the bar)

Is negative because mass 1 is to the left of the coordinate system (see the diagram)

Position and momentum.
This is Heisenberg's Uncertainty Principle:
Δx Δp ≥ h ÷ 4π, where Δx is the change in position, Δp is the change in momentum, and h is Planck's Constant.