A sonar emits a sound signal of frequency 40000Hz, towards the bottom of the sea. This signal is reflected on the body of a submarine after a delay of 0.3 seconds.
Given: Speed of sound in water is 1500 m/s.

Calculate the period of this wave.

Jason and mia are both running in a race. as they approach the finish line, you being the physicist that you are decide to time how long it takes them to reach the end of the race. when you start your stop watch (you can take this as time t = 0 s) you notice that mia is an unknown distance d ahead of jason and both are moving with the same initial velocity v_0. you also notice that jason is accelerating at a constant rate of a_j, while mia is deaccelerating at a constant rate of -a_m. jason and mia meet each other for the first time at time t = t_1. at this time (t = t_1) jason's velocity is two times that of mia's velocity, meaning v_j (t_1) = 2v_m (t_1). a) draw the position vs. time graph describing mia's and jason's motion from time t = 0 to time t = t_1. clearly label your axes and initial conditions on your graph. b) draw the velocity vs. time graph describing mia and jason's motion from time t = 0s to time t = t_1. clearly label your axes and initial conditions on your graph. c) how long from when the stop watch was started at t = 0s did it take mia and jason to meet? express your answer in terms of know quantities v_0, a_m, and a_j. d) when the stop watch started at time t = 0s, how far apart, d, were mia and jason? express your answer in terms of know quantities v_0, a_m, and a_j.

5g of ammonium nitrate was dissolved in 60g of water in an insulated container. the temperature at the start of the reaction was 23.0°c and at the end it was 19.0°c. calculate the energy absorbed by the reaction.

You've already seen the value of 9.8 in this lesson. what's this value called? what quantity does it represent?