Why is a convex lens useful for starting fires

Why does an object in motion stay in motion unless acted on by an unbalanced force? A) because forces are what stop and start motion B) because balanced forces can not exist in nature C) because motion is the inherent state of all matter D) because

What is true about empirical and molecular formulas?

At table tennis ball has a positive charge of 4.50 * 10-8 coulombs. It experiences a force of 2.72 * 10-3 newtons due to an electric field. What is the strength of the electric field? 2.72 * 10-10 newtons/coulomb 4.50 * 10-11 newtons/coulomb 6.

If a person lives in china in which two hemispheres does he or she live

I drop a penny from the top if tower at the front of Fort Collins high school and it takes 1.85 seconds to hit the ground calculate the velocity in m/s after 1.10 seconds of frefall and calculate the velocity at Impact I'm mi/hr

A wire carrying a 2-A current is placed at an angle of 60° with the respect to a magnetic field of strength 0.2 T. If the length of the wire is 0.6 m what is the magnitude of the magnetic force acting on the wire?

A meteorologist wants to measure the temperature. Which weather instrument should the meteorologist use? a. a barometer b. a rain gauge c. a thermometer d. a weather vane

Calculate the mass defect of the helium nucleus 42He. The mass of neutral 42He is given by MHe=4.002603u.

A person lifts a 4.5 kg cement block a vertical distance of 1.2 m and then carries the block horizontal - ly a distance of 7.3 m. determine the work done by the person and by the force of gravity in this process.

A tree is standing in the middle of a meadow. As you watch, the wind begins to blow and the tree bends. Which statement best explains how you could tell that a net force was acting on the tree? OA) The tree had momentum.