What do keplers laws describe?
a. the forces between any two objects
b. the effect of mass on gravity
c. the shape of an orbit
d. the effects of gravity

Aspring is used to stop a 50-kg package which is moving down a 20º incline. the spring has a constant k = 30 kn/m and is held by cables so that it is initially compressed 50 mm. knowing that the velocity of the package is 2 m/s when it is 8 m from the spring and neglecting friction, determine the maximum additional deformation of the spring in bringing the package to rest.

Would it be correct to say the doppler effect is the apparent change in the speed of a wave due to the motion of the source? be sure to fully explain your position using at least 3 complete content related sentences.

Which of the following is not an appropriate unit for acceleration? (kg/12 mihr? m/min/sec cm/30c?