A high-voltage dc overhead cable carries a current of 2000 A. One 20 m section of the cable has a mass of 120 kg. This cable section is supported so…

A submarine uses sound of frequency 6000 Hz to locate obstructions ahead of it in the sea. A pulse of this sound reflects off an object that is 750 m…

A water jet pack has lifted a person vertically upwards, as shown in the sketch. He is now stationary at a constant height. Water rises through the tube and is…

The radioactive isotope plutonium-244 becomes radon-220 after a succession of decays. The atomic number of plutonium is 94 and the atomic number of radon is 86. How many alpha particles…

A book rests on a table, which in turn rests on the floor. The floor exerts a force P on the table. Force P and one other force constitute a…

An object that has a weight of 15 N on Earth is taken to a planet where it has a weight of 3.0 N.The planet has no atmosphere. Which line…

A car is being driven at 20 m / s when the driver sees a child run into the road. The driver’s usual reaction time is 0.70 s, but this…