Answer:
80%
Explanation:
Efficiency of machine = work output/work input ×100 %
From question, work output = 20J
Work input = 25J.
Therefore efficiency = 20/25 × 100 %
Efficiency = 20×4 %
Efficiency = 80%
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Answer:
9.45 kWh
Explanation:
Energy = Power × time
E = 900 W × (1.5 h/day × 7 day)
E = 9450 Wh
E = 9.45 kWh
V o - initial velocity
v = velocity at the maximum height,
v² = v o² - 2 g h
v = 0
0 = v o² - 2 g h
v o² = 2 g h = 2 · 9.80 · 0.460
v o² = 9.052
v o = √9.052 = 3.004197 m/s ≈ 3 m/s
Answer:

Explanation:
Kinetic energy is energy due to motion. The formula is half the product of mass and velocity squared.

The mass of the roller coaster car is 2000 kilograms and the car is moving 10 meters per second.
Substitute these values into the formula.

Solve the exponent.
- (10 m/s)²= 10 m/s * 10 m/s= 100 m²/s²

Multiply the first two numbers together.

Multiply again.

- 1 kilogram square meter per square second is equal to 1 Joule.
- Our answer of 100,000 kg*m²/s² is equal to 100,000 Joules.

The roller coaster car has <u>100,000 Joules</u> of kinetic energy.