Q1. The driver of an 1800 {kg} car travelling on a horizontal road at 100 kmh suddenly applies the brakes. Because of a slippery pavement, the friction of the road on the tires of the car, which is what slows down the car, is 20.0 percent of the weight of the car.
What is the acceleration of car?
Q2. A 1400 {rm kg} wrecking ball hangs from a 16 {rm m}-long cable. The ball is pulled back until the cable makes an angle of 27.0^circle with the vertical. By how much has the gravitational potential energy of the ball changed?