Forces and Kinematics

A block of mass 3 kg, initially at rest, is pulled along a frictionless, horizontal surface with a force shown as a function of time t by the graph above.

The speed of the block at t = 2s is

• 4/3 m/s

• 8/3 m/s

• 4 m/s

• 8 m/s

• 24 m/s

Tags

NGSS.HS-PS2-1

The position of an object is given by the equation x = 3.0 t2 + 1.5 t + 4.5, where x is in meters and t is in seconds. What is the instantaneous acceleration of the object at t = 3.0 s?

• 3.0 m/s/s

• 6.0 m/s/s

• 9.0 m/s/s

• 19.5 m/s/s

• 36 m/s/s

Tags

NGSS.HS-PS2-1

The position of a toy locomotive moving on a straight track along the x-axis is given by the equation x = t³ – 6t² + 9t, where x is in meters and t is in seconds. The net force on the locomotive is equal to zero when t is equal to

• zero

• 2 s

• 3 s

• 4 s

• 5 s

Tags

NGSS.HS-PS2-1

The momentum p of a moving object as a function of time t is given by the expression p = kt³, where k is a constant. The force causing this motion is given by the expression

• 3kt²

• 3kt²/2

• kt²/3

• kt⁴

• kt⁴/4

Tags

NGSS.HS-PS2-1

An object weighing 300 N is suspended by means of two cords, as shown above. The tension in the horizontal cord is

• 0 N

• 150 N

• 210 N

• 300 N

• 400 N

Tags

NGSS.HS-PS2-1

Three blocks of masses 3m, 2m, and m are connected to strings A, B, and C as shown above. The blocks are pulled along a rough surface by a force of magnitude F exerted by string C. The coefficient of friction between each block and the surface is the same. Which string must be the strongest in order not to break?

• A

• B

• C

• They must all be the same strength

• It is impossible to determine without knowing the coefficient of friction

Tags

NGSS.HS-PS2-1

A skier slides at constant speed down a slope inclined at an angle ϕ to the horizontal, as shown above. If air resistance is negligible, the coefficient of friction µ between the skis and the snow is equal to

• 1/tanϕ

• 1/cosϕ

• sinϕ

• cosϕ

• tanϕ

Tags

NGSS.HS-PS2-1

A block of mass m is placed against the inner wall of a hollow cylinder of radius R that rotates about a vertical axis with a constant angular velocity ω, as shown above. In order for friction to prevent the mass from sliding down the wall, the coefficient of static friction μ between the mass and the wall must satisfy which of the following inequalities?

• 
• 
• 
• 
• 

Tags

NGSS.HS-PS2-1

Three identical disks are initially at rest on a frictionless, horizontal table with their edges touching to form a triangle, as shown in the top view above. An explosion occurs within the triangle, propelling the disks horizontally along the surface. Which of the following diagrams shows a possible position of the disks at a later time? (In these diagrams, the triangle is shown in its original position.)

• 
• 
• 
• 
• 

Tags

NGSS.HS-PS2-1

NGSS.HS-PS2-2

A person is standing at one end of a uniform raft of length L that is floating motionless on water, as shown above. The center of mass of the person-raft system is a distance d from the center of the raft. The person then walks to the other end of the raft. If friction between the raft and the water is negligible, how far does the raft move relative to the water?

• L/2

• L

• d/2

• d

• 2d

Tags

NGSS.HS-PS2-2