PROBLEMS
- A 2.0 kg block rests on a horizontal surface. A horizontal force of 6.0 N is applied to the block. If the coefficient of static friction between the block and the surface is 0.40, will the block move? Explain, including the math.
- A 5.0 kg box is sliding on a 25-degree incline with a coefficient of kinetic friction between the box and the incline of 0.25. Calculate the acceleration of the box both while sliding downward and while sliding upward on the incline.
- An object with a mass of 3.0 kg is in free fall near the Earth's surface. Calculate the gravitational force acting on the object. Then, if the same object were magically transported to the surface of a planet with three times the Earth's mass and twice the Earth's radius, what would the new gravitational force on the object be?
- A 75 kg student is standing on a bathroom scale inside an elevator. If the elevator is accelerating upwards at a rate of 1.5 m/s2, what will the scale read?
- Two blocks, with masses m1 = 4.0 kg and m2 = 6.0 kg, are connected by a light string that passes over a frictionless pulley. The system is released from rest. Determine the acceleration of each block and the tension in the string.
- A 1.5 kg book rests on a table. You push down on the book with a force of 5.0 N. What is the normal force exerted by the table on the book?
- A car of mass 1200 kg is traveling at a constant speed of 25 m/s on a level road. The total friction and air resistance force acting on the car is 800 N. What force must the engine produce through the tires to propel the car. What is the direction of the force by the tires on the ground?
- A small object (treat as a point mass) with mass of 0.1 kg is located a distance of 0.5 m away from a bowling ball (mass 7.0 kg). Calculate the gravitational force of attraction between the two objects.
- A 3.0 kg block is pulled up a 30-degree incline by a force of 25 N acting parallel to the incline. If the block starts from rest at the bottom of the incline and the coefficient of kinetic friction is 0.20, what is the block's speed after traveling 2.0 meters along the incline?
- Describe what is wrong with the following equation, and then provide a corrected version if applicable, or explain why no correction is possible: , where N is the normal force and is the weight.
ANSWERS
- No, the block will not move, because the maximum force of static friction exceeds the applied force.
- Downward: 2.24 m/s2; Upward: -7.48 m/s2
- 29.4 N; 33.1 N
- 862.5 N (or 863N)
- a = 1.96 m/s2, T = 47.0 N
- 19.7 N (or 20N using g=10)
- 800 N
- 1.86 × 10-10 N
- 2.0 m/s (or 2.05 m/s if g = 9.8)
- N is a scalar while W is a vector and so must have direction. A correct version is |N|=|W|.