Finals Questions

A 1000 kg car sits on a ramp that is tilted at angle  θ = 24◦ above the horizontal. Find the numerical value for the minimum coefficient of static friction μ between the surface of the block and the ramp, below which the block starts to slide.

• 0.45

• 0.91

• 0.41

• 0.74

A 1200 kg truck is parked on a slope inclined at an angle θ = 30◦ to the horizontal. Determine the minimum coefficient of static friction μ required between the truck's tires and the slope to prevent it from sliding down.

• 0.50

• 0.87

• 0.58

• 0.65

You push a light object of mass m and a heavy object of mass M = 3m with the same force F. What is the relationship between the acceleration a of the light object and the acceleration A of the heavy object?

• A = a

• A = 3 a

• A = (1/3) a

• A = (1/9) a

You apply the same force F to two objects, one with mass m and the other with mass 2m. What is the relationship between the acceleration a of the object with mass m and the acceleration A of the object with mass 2m?

• A = a

• A = 2 a

• A = (1/2) a

• A = (1/4) a

A Lotus Elise sports car accelerates from 0 miles per hour to 60 miles per hour in 4.2 seconds. What will the car’s displacement be when it reaches 60 miles per hour?

• 252 mi

• 2.1 mi

• 126 mi

• 0.035 mi

A Porsche sports car accelerates from 0 miles per hour to 80 miles per hour in 5 seconds. What will the car’s displacement be when it reaches 80 miles per hour?

• 400 mi

• 3.5 mi

• 200 mi

• 0.06 mi

Abeera, standing on the ground, throws a ball straight up. The ball goes to a height of  3 meters above her hand before she catches it at the same height at which it was thrown. Assume  air resistance is negligible. What is the acceleration a of the ball while it is in the air? What was the initial velocity v_i of the ball? How long (t) was the ball in the air? (SHOW YOUR WORK)

• a = -9.8 m/s²; v_i = 7.67 m/s; t = 1.56 s

• a = 9.8 m/s²; v_i = 7.67 m/s; t = 0.78 s

• a = -9.8 m/s²; v_i = 7.67 m/s; t = 0.78 s

• a = -9.8 m/s²; v_i = 5.42 m/s; t = 1.10 s

A ball is thrown straight up and reaches a maximum height of 6.7 m above its release point, before being caught back at the original position. Assume  air resistance is negligible. What is the acceleration a of the ball while it is in the air? What was the initial velocity v_i of the ball? How long (t) was the ball in the air? (SHOW YOUR WORK)

• a = -9.8 m/s²; v_i = 11.5 m/s; t = 2.34 s

• a = 9.8 m/s²; v_i = 11.5 m/s; t = 1.17 s

• a = -9.8 m/s²; v_i = 11.5 m/s; t = 1.17 s

• a = -9.8 m/s²; v_i = 8.1 m/s; t = 1.65 s

You are moving into a new dorm and  push a 10 kg box into your room. You start pushing the box parallel to the floor, and gradually increase your force until the box starts to move. What is the Normal force F_N of the floor on the box? You borrow a force probe from a physicist and measure the applied force right before the box starts moving. It is 60 N. Calculate the static friction coefficient μ_s between the box and the floor? (SHOW YOUR WORK)

• F_N = 98 N; μ_s = 0.6

• F_N = 98 N; μ_s = 0.17

• F_N = 60 N; μ_s = 0.6

• F_N = 60 N; μ_s = 0.17

What is approximately the coefficient of static friction if it takes 40 N of force to move a box of mass 8 kg? (SHOW YOUR WORK)

• 0.51

• 0.20

• 0.82

• 0.63