Unit 4 Practice Test Flashcards
A cart weighing 5 N is pushed a distance of 7.5 m by a constant force of 3 N. There is no friction between the cart and the track it is on. Which of the following is the amount of work done by the force?
22.5 J
A meteorite with a mass of 25 kilograms falls to Earth in a direction perpendicular to the Earth’s surface. At t = 0 seconds the meteorite is 1000 meters above the Earth. At t = 2 seconds it is 750 meters above the Earth. Assume the meteorite’s acceleration due to gravity is constant during this time. Which of the following is the amount of work the Earth’s gravitational force has done on the meteorite between t = 0 and t = 2?
61,250 J
A rope that makes a 15 degree angle with the horizontal pulls a block weighing 3N a distance of 10 meters to the right at a constant velocity. The tension in the rope is a 2N force. How much work is done by the rope acting on the block in the horizontal direction? Let Fx be the tension in the rope and delta x be the displacement in the x-direction.
19.32 J
Two ropes are pulling on a box. The first rope is pulling the box from the right and is parallel to the floor. The second rope, pulling from the left, forms a 110 degree angle with the first rope. If the tension in the second rope is 5N and the box moves 3 meters to the left, what is the work done by the second rope on the box? Let FL be the tension in rope pulling from the left and delta x the displacement
5.13 J
For a variable force acting on an object from Position 1 to Position 2, the work done can be approximated by W = sigma Fx delta x. How can the approximation be improved.
By making delta x smaller
Suppose a force F = 3x^2 N is acting on an object that undergoes a displacement from x = 1m to x = 2m. What is the work done on the object?
7 J
Which of the following expresses the work done by a spring on an object that moves from position xi to xf ?
W = integral from xi to xf of (-kx)dx
If we decrease the displacement of an object attached to a spring, the magnitude of the force on the object __________________.
decreases
How is the kinetic energy of an object affected if its velocity is doubled?
The kinetic energy is quadrupled.
In kinematics, the final velocity vf of an object undergoing constant acceleration is given by which of the following equations?
vf^2 = vi^2 + 2ax delta x
A bobsled team begins at the top of a frozen track that runs down a hill that is 0.2 km tall. The total length of the track as it winds its way down the hill is 1.2 km. Ignoring friction, how fast is the bobsled moving when it gets to the finish line?
63 m / s
Suppose you push with a constant force on a box with a mass of 20 kg and it moves at a constant speed of 1.5 m / s along a horizontal surface. How much force are you using on the box? The coefficient of sliding friction is 0.5.
98 N
A 50 kg girl runs up a staircase in 20 s, and a 60 kg boy runs up the same staircase in 15 s. Which of the following is the ratio of the power generated by the girl to the power generated by the boy?
5 : 8
A variable force described by the equation
F (t) = at 2 + 5bt, where a and b are positive constants, moves an object 4 m in 3 s. The force is directed in the direction of motion of the object. Which of the following is the average power used to move the object?
24a + 20b
If an object is shot straight up in the air with a velocity of 5 m / s, how high will it go?
1.3 m
