Forces
This is responsible for the slowing down of a toy car as it rolls across the floor.
What is friction?
What are forces commonly acting on a system in free fall?
What is gravitational force?
A 6-kg block is pulled along a horizontal floor by a force ๐โ = (30 ๐)๐ฬ+ (40 ๐)๐ฬ. The +x direction is to the right and the +y direction is upward. What is the normal force on the box?
What is 20 N?
A box is on top of a horizontal floor. A force ๐นโ that makes an angle theta below the horizontal is applied to the box. If the angle theta is increased somewhat, what happens to the forces on the box? Draw the FBD as proof
Both the normal force and maximum static frictional force increase
A person runs 400 m north and then 250 m west. The time it takes for the entire run is 100 s. What is the magnitude of the average velocity for the entire run?
What is 4.7 m/s?
The gravitational force on an object is also known as this.
What is weight?
A projectile is launched at an upward angle of 30 degrees to the horizontal with a speed of 30 m/s. How does the horizontal component of its velocity 1.0 s after launch compare with its horizontal component of velocity 2.0 s after launch, ignoring air resistance?
What is the horizontal component stays the same?
A carnival merry-go-round rotates about a vertical axis at a constant rate. A man standing on the edge has a constant speed of 3 m/s and moves along a circular path. If the radius of this circular path is 4 m, then the acceleration of the man is
What is 2.25 m/s2?
Calculate the static frictional force of a 130 kg statue when pushed across a floor where the coefficient of friction is 0.25. Include the FBD as proof
Ff = 318.5 N
A particle moves so that its position (in meters) as a function of time (in seconds) is ๐โ = (5๐ก)๐ฬ+ (3๐ก 2 )๐. What is the speed of the particle at t = 1.2 s?
What is 8.8 m/s?
This force is perpendicular to surfaces in contact usually opposes gravity or its component.
What is normal force?
One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level?
What is the second ball?
You throw a ball towards a wall at speed 24 m/s and at angle = 38ยฐ above the horizontal. The wall is distance d = 18 m from the release point of the ball. Ignore air resistance. What is the acceleration of the ball just before it hits the wall? Put your answer in unit vector notation.
What is (โ10 ๐/๐ 2 )๐ฬ?
Draw a diagram of a 100 kg box on a flat surface being pulled to the right with a force of 300 N and experiencing a frictional force of 250 N. What is acceleration? What is the coefficient of friction?
a. a = 0.5 m/s2
b. mu = 0.255
Two airplanes are flying at the same altitude over level ground. Plane A is traveling with a horizontal velocity of 250 km/h, while Plane B is flying with a horizontal velocity of 560 km/h. Both planes release a bundle of food supplies at the same time. Which bundle will hit the ground first? Ignore air resistance
Both bundles hit the ground at the same time
A ratio of the frictional force and normal force on an object is this.
You are riding in an enclosed train car moving at 90 km/h. If you throw a baseball straight up, where will the baseball land?
What is the baseball will land in your hand?
Block A in the figure has a mass mA = 4.6 kg, and block B has mass mB = 3.4 kg. The coefficient of kinetic friction between block B and the horizontal plane is uk = 0.4. The inclined plane is frictionless and at angle = 35ยฐ. The cord has negligible mass. Once the blocks are released, block A slides down the inclined plane and block B slides to the left. What is the acceleration of block A as it slides down the inclined plane?
What is 1.6 m/s2?
A particle is moving in the counterclockwise direction along a circular path at a constant speed. In what direction does the acceleration of an object act? Support your answer with a FBD
What is towards the center of the circular motion?
You are pushing a box in the positive direction with increasing speed along a horizontal floor. Friction acts on the box. At t = 0, you suddenly stop pushing the box. Draw the velocity versus time graph that depicts the scenario.
The formula for centripetal force acting on a sliding, turning object.
What is F = mv2/r?
An object is traveling at a constant velocity in the +y direction. Then, a net force in the +x direction acts on the object. Identify the true statement(s).
a. While the net force is applied, the x component and the y component of the acceleration are both positive.
b. While the net force is applied, the x component of the acceleration is positive, but the y component is zero.
c. While the net force is applied, the y component of the velocity decreases.
d. Both (a) and (c)
e. Both (b) and (c)
What is (b) while the net force is applied, the x component of the acceleration is positive, but the y component is zero?
Block A in the figure has a mass mA = 4.6 kg, and block B has mass mB = 3.4 kg. The coefficient of kinetic friction between block B and the horizontal plane is uk = 0.4. The inclined plane is frictionless and at angle = 35ยฐ. The cord has negligible mass. Once the blocks are released, block A slides down the inclined plane and block B slides to the left. What is the tension in the cord as block A slides down the inclined plane?
What is 19 N?
A 60-kg block is at rest on a horizontal floor. The maximum static frictional force between the block and the floor is 130 N. A horizontal force with a magnitude of 130 N is applied to the block. What is the acceleration of the box?
What is 0 m/s2?
A box is initially at rest on a horizontal surface. Starting at t = 0 s, you exert a constant, horizontal force on the box, and the box begins to move. As the box slides, kinetic friction acts on it. Describe how the speed of the box and the frictional force on the box vary while you are pushing the box.
What is the speed increases the entire time and friction stays the same?