the useful power out of an electric motor is 20w and the total power into the motor is 80w calculate the percentage efficiency of the motor

A boat in a race accelerates uniformly at 0.2 m/s² for 18 seconds to reach a final speed of 6 m/s. Work out the initial speed of the boat.

Question 1 Unsaved Most of the mass of the solar system is located in which of the following? Question 1 options: Earth comets sun Jupiter

What is the cooling power P? Recall that the rate at which energy is removed, also called the cooling power, was described earlier as being constant. Express your answer numerically in watts (joules per second).

If a wave has a frequency of 2 Hz. what is the period

Sam's bike tire contains 15 units of air particles and has a volume of 160mL. Under these conditions the pressure reads 13 psi. The tire develops a leak. Now it contains 10 units of air particles and has contracted to a volume of 150mL.

What is the process in which the work of scientists is evaluated by other researchers? a. Scientific critique c. scientific inquiry b. Peer review d. Inquisition

A gust of wind blowing east pushes against a ball. When will the wind do work on the ball?

What is the emf of a battery that increases the electric potential energy of 0.060 CC of charge by 0.70 JJ as it moves it from the negative to the positive terminal?

Which of the following statements is true? A. Minerals can be solids or liquids B. Minerals can be elements or compounds C. Graphite and gold are examples of gemstones D. Triclinic crystals have more right angles than isometric crystals

Stu wanted to calculate the resistance of a light bulb connected to a 4.0-V battery, with a resulting current of 0.5 A. He used the formula R = VI and obtained an answer of 2. Was Stu's answer correct? How do you know?