What would you need to do to find an object's mass and velocity? what tools do you need

Your target variable is δf, the magnitude of the difference in frequency between the waves emitted from the sonar device and the waves received by the device after reflecting off the whale. write an expression for δf in terms of the relevant frequencies using the subscript notation introduced above.

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?

Abookcase has a mass of 38 kg and the coefficient of friction between it and the floor is 0.82 what is the maximum force of friction between the bookcase and the floor a 372n b 305n c 412n d 449n