A little boy rides a roller coaster that makes a loop with a radius of 30.0m. The boy hits the bottom of the loop traveling at 40.0m/s. The net force on the boy is 1350N. What is the mass of the boy? 1800 kg
60 kg
1010 kg
25.3 kg

An electron is traveling with initial kinetic energy k in a uniform electric field. the electron comes to rest momentarily after traveling a distance d. (a) what is the magnitude of the electric field

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".

Efficiency is the ratio of to for a system a)power in to power in b)power in to power out c) power out to power out d) power out to power in