Please help me these questions a. A bus slams on its brakes and goes from 30 km/hr to 15 km/hr in 4 seconds. What is its acceleration? b. If a car with an initial speed of 10 m/s, accelerates at a rate of 50 m/s2 for 3 seconds. What will be the final speed be? c. A force of 100 newtons accelerates a mass of 5 kg for 10 seconds. If the mass is initially at rest, calculate the final velocity. d. A 5 kg block is pulled across a table by a horizontal force of 40 N with a frictional force of 8 N opposing the motion. Calculate the acceleration of the object.