1. When you push a box along the floor with a force of 8 N, the box moves at constant speed due to the friction force between the floor and box. When you push the same box (which is subject to the same friction force) with a force of 10 N, the box accelerates at 3.5 m/s². What is the mass of the box? (in kg)

2. A ball that is dropped from rest is falling down. When the ball hits the ground it has a speed of 10 m/s. What is the speed of the ball (in m/s) half-way to the ground? Neglect air friction.

3. Two wooden crates, one of mass m₁ and the other one of three times larger mass m₂ =3 m₁, are connected by a rope that passes over a pulley as shown in the figure.

m m2