When placed at a certain point, a 4.20 C charge feels an electric force of 2.55 N. What is the magnitude of the electric field at that point?
(Remember, magnitudes are always positive.) (Unit = N/C)

Arunner is jogging at a steady 3.6 km/hr. when the runner is 2.9 km from the finish line, a bird begins flying from the runner to the finish line at 14.4 km/hr (4 times as fast as the runner). when the bird reaches the finish line, it turns around and flies back to the runner. even though the bird is a dodo, we will assume that it occupies only one point in space, i.e., a zero-length bird. how far does the bird travel? (b) after this first encounter, the bird then turns around and flies from the runner back to the finish line, turns around again and flies back to the runner. the bird repeats the back and forth trips until the runner reaches the finish line. how far does the bird travel from the beginning? (i.e. include the distance traveled to the first encounter)

Asatellite that goes around the earth once every 24 hours iscalled a geosynchronous satellite. if a geosynchronoussatellite is in an equatorial orbit, its position appearsstationary with respect to a ground station, and it is known as ageostationary satellite find the radius rof the orbit of a geosynchronous satellite that circles the earth.(note that ris measured from the center of the earth, not the surface.) you mayuse the following constants: the universal gravitational constant g is 6.67 \times 10^{-11}\; {\rm n \; m^2 / kg^2}. the mass of the earth is 5.98 \times 10^{24}\; {\rm kg}. the radius of the earth is 6.38 \times 10^{6}\; {\rm m}.

The radioactive isotope of lead, pb-209, decays at a rate proportional to the amount present at time t and has a half-life of 3.3 hours. if 1 gram of this isotope is present initially, how long will it take for 80% of the lead to decay? (round your answer to two decimal places.)