Physics Questions & Answers

Physics Questions & Answers A 0.5kg object is in free fall as it falls downward near the surface of a planet. A graph of the object's velocity as a function of time is shown. What is the force due to gravity exerted on the object by the planet? - CORRECT ANSWER- 1.25N A 100 kg cart goes around the inside of a vertical loop of a roller coaster. The radius of the loop is 3 m and the cart moves at a speed of 6 m/s at the top. The force exerted by the track on the cart at the top of the loop is - CORRECT ANSWER- 200 A 2kg object is initially at rest at time t=0s. It then slides across a rough, horizontal surface under the influence of only the four forces shown in the table above. What is the speed of the object at time t=3s ? - CORRECT ANSWER- 36 A 50.0 N box is at rest on a horizontal surface. The coefficient of static friction between the box and the surface is 0.50, and the coefficient of kinetic friction is 0.30. A horizontal 20.0 N force is then exerted on the box. The magnitude of the acceleration of the box is most nearly - CORRECT ANSWER- 0 A 5kg object is released from rest near the surface of a planet. The object's vertical position as a function of time is shown in the graph. Which of the following procedures can be used to determine the strength of the gravitational field on the planet? - CORRECT ANSWER- Use y=y0+vy0t+12ayt2. Use 10s for t, 0 ms for vy0, 400m for y0, and 0m for y. Solve for ay. A ball is moved from Earth to a planet that has a gravitational acceleration that is double that of Earth. How does the gravitational force on the ball when it is on the new planet compare to the gravitational force on the ball when it is on Earth? - CORRECT ANSWER- The gravitational force on the ball when it is on the new planet is double the force on the ball when it is on Earth. A ball of mass m is attached to a vertical rod by two massless strings. The rod is rotated about its axis so that both strings are taut, with tensions T1 and T2, respectively. The strings and rod form the right triangle shown in the figure above. The ball rotates in a horizontal circle of radius rwith speed v. What is the magnitude of the net force on the ball? - CORRECT ANSWER- mv^2 / r A ball of mass m is found to have a weight Wx on Planet X. Which of the following is a correct expression for the gravitational field strength of Planet X? - CORRECT ANSWER- The gravitational field strength of Planet X is Wx/m. A ball of mass M is on a horizontal surface with negligible friction. One end of a string is attached to the ball so that it is spun in a horizontal circle of radius R at tangential speed v0, as shown in Figure 1. A free-body diagram for the ball at an instant in time is shown in Figure 2. The magnitude of the tension force is also indicated in Figure 2. Which of the following equations represents the centripetal acceleration of the ball if its tangential speed is increased to 2v0? - CORRECT ANSWER- ac=4vo^2/R