.Why is topsoil darker than all other levels of soil?

Abaseball picther can throw a ball at about 90 miles per hour, v = 40 m/s, on solid rock ground. we now put him into space. when he throws the ball, which weighs mb = 0.15 kg moves away from himat the same speed. how long does it take the ball thrown in space to travel the 30 meters to the batter? he weighs mp = 100kg

Erosion of the beach is normally a slow process. however, in certain situations, large chunks of shore may wash out to sea. what could cause this to happen?

A2k pendulum has a speed of 1 m/s at a height of 1/2 meter