Question 1 (3 points)
Use Newton’s second law of motion to solve the following problems.
- A car accelerates forward at 3.5 m/s2. If the car has a mass of 873 kg, what is the force applied to the car? (1 point)
- Ron bicycles forward with an acceleration of 2.1 m/s2. If he is applying a forward force of 195 N, what is his mass? (1 point)
- What is the acceleration of a skateboarder of mass 46 kg who is being pushed forward with a force of 120 N? (1 point)
Question 2 (1 point)
A mountain lion has a mass of 65 kg. What is the weight of the mountain lion, in newtons? (1 point)
Question 3 (1 point)
A car of mass 1500 kg drives in a circle with a constant speed of 18 m/s. What is the radius of the circle if the centripetal force on the car is 3313.6 N? (1 point)
Question 4 (5 points)
Dave and Alex push on opposite ends of a car that has a mass of 875 kg. Dave pushes the car to the right with a force of 250 N, and Alex pushes to the left with a force of 315 N. Assume there is no friction.
- Draw a free-body diagram showing all the forces acting on the car. (2 points)
- What is the net force on the car in the x-direction? (1 point)
- What is the acceleration of the car? (1 point)
- What is the normal force acting on the car? (1 point)
Question 5 (5 points)
A water-skier is pulled behind a boat by a rope that is at an angle of 13° and has a tension of 490 N. The water-skier has a mass of 49 kg.
- Draw a free-body diagram showing the forces acting on the skier. (She is being pulled to the right.) (2 points)
- What are the magnitudes of the x- and y-components of the tension? (2 points)
- What is the normal force acting on the skier? (1 point)
Question 6 (5 points)
Your dog sleeps on the floor. He has a mass of 14 kg. The coefficient of static friction between him and the floor is 0.3, and the coefficient of kinetic friction is 0.25.
- What is the weight of your dog? (1 point)
- What is the normal force acting on your dog? (1 point)
- What is the maximum force of static friction? (1 point)
- You push horizontally on your dog with a force of 50 N. Does your dog slide? (1 point)
- Later, you are sliding your dog across the floor at a speed of 2 m/s. What is the force of kinetic friction acting on your dog? (1 point)
Question 7 (5 points)
Blaine steps onto a ski slope with an angle of 25°. There is a coefficient of kinetic friction of 0.15 between him and the ground. He has a mass of 65 kg.
- Draw the free-body diagram showing the forces acting on Blaine. (1 point)
- Write the expressions for net force in the x- and y-directions. Be sure to tilt your axis along the incline. (2 points)
- Calculate the net force and acceleration in the x- and y- directions. (2 points)