Inclined Planes

A 4.0-kg box sits on a frictionless inclined plane that makes a 21° angle with the horizontal. It is held in place by a cord parallel to the plane. Calculate the tension in the cord.

Pushing a 10-kg toolbox across the floor, you find that the box moves at a constant speed when you push horizontally with a force of 39 N. What is the coefficient of kinetic friction between the floor and the toolbox?

You push on a 3-kg box to give it an initial speed of 5 m/s across a floor. If μ_k = 0.3, how far does the box travel before coming to a stop?

A 36N force is needed to start a 7.0 kg box moving across the floor. If the 36.0 N force continues, the box accelerates at 0.70 m/s². What are the coefficients of static and kinetic friction?

A 3-kg block is at rest on an adjustable ramp. When the ramp is tilted to a 20° angle, the block slides with constant velocity. What is the coefficient of kinetic friction between the ramp and the block?

Two blocks are connected by a cord over a pulley. Block A rests on a rough tabletop. Block B has mass mB=2kg and hangs over the edge of the table. The coefficients of friction between Block A and the tabletop are μs=0.6 and μk=0.4. What is the minimum mass Block A can have to keep the system from starting to move?

Two blocks made of different materials, connected by a string, slide down a 30° inclined plane . Block A has mass 8kg, and the coefficient of static friction between Block A and the incline is 0.35. Block B has mass 4kg, and the coefficient of friction between block B and the plane is 0.25. After the blocks are released, find the tension in the cord.

A 4kg block sits on top of a 6kg block which is on a frictionless surface. The coefficients of friction between the two blocks are μs=0.5 and μk=0.3. Calculate the maximum force you can pull on the bottom block with so that the objects move together.

A vertical spring is originally 60 cm long. When you attach a 5 kg object to it, the spring stretches to 70 cm. 

(a) Find the force constant on the spring.
(b) You now attach an additional 10 kg to the spring. Find its new length.

(For the multiple choice selection, answer only part (b). Use g=10 m/s².)