Physics
Question 1 (3 points)
Use Newton’s second law of motion to solve the following problems.
a. 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)
b. 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)
c. 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.
a. Draw a free-body diagram showing all the forces acting on the car. (2 points)
b. What is the net force on the car in the x-direction? (1 point)
c. What is the acceleration of the car? (1 point)
d. 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.
a. Draw a free-body diagram showing the forces acting on the skier. (She is being pulled to the right.) (2 points)
b. What are the magnitudes of the x- and y-components of the tension? (2 points)
c. 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.
a. What is the weight of your dog? (1 point)
b. What is the normal force acting on your dog? (1 point)
c. What is the maximum force of static friction? (1 point)
d. You push horizontally on your dog with a force of 50 N. Does your dog slide? (1 point)
e. 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.
a. Draw the free-body diagram showing the forces acting on Blaine. (1 point)
b. Write the expressions for net force in the x- and y-directions. Be sure to tilt your axis along the incline. (2 points)
c. Calculate the net force and acceleration in the x- and y- directions. (2 points)
