A 20 kg box is being pulled across a floor by a horizontal rope. The tension in the rope is 99 Newtons. The coefficient of friction is 0.25. What is the force of friction on the box? What is the acceleration of the box?

A10.0 kg cart and a 15kg cart are locked together with a compressed spring between them. they are then released so that the spring pushes the two carts apart. the 10.0 kg cart is moving at 4.5 m/s afterward. how fast is the 15kg cart moving? 3.0 m/s 2.0 m/s 4.5 m/s 5.0 m/s

If it takes a planet 2.8 x 10^8 s to orbit a star with a mass of 6.2 x 10^30 kg what is the average distance between the planet and the star

Could someone . i have tried to solve myself but my calculation is off