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# Physics problems:dynamics

Part 5

Problem 41.

A 1.5 kg mass is attached to the end of a 90 cm string. The system is whirled in a horizontal circular path. The maximum tension that the string can withstand is 400 N. What is the maximum number of revolutions per minute allowed if the string is not to break?

Solution

Problem 42.

The force required to stretch Hooke's Law spring varies from 0 N to 65 N as we stretch the spring by moving one end 6.3 cm from its unstressed position. Find the force constant of the spring. Answer in units of N/m.

Solution

Problem 43.

A 100 kg load is placed on a 40 kg stretcher to be carried by two persons. The stretcher is 2m long and the load is placed 0.6m from the left end. How much force must each person exert to carry the stretcher?

Solution

Problem 44.

A painter weighing 900 N stands on a massless plank 5 m long that is supported at each end by a stepladder. If he stands 1m from one end of the plank, what force is exerted by each stepladder?

Solution

Problem 45.

A 20 kg child and a 30 kg child sit at opposite ends of a 4 m seesaw that is pivoted at its center. Where should another 20 kg child sit in order to balance the seesaw?

Solution

Problem 46.

A hotel guests starts to pull an armchair across a horizontal floor by exerting a force of 91 N 15 degrees above the horizontal.  The normal force exerted by the floor on the chair is 221 N up.  The acceleration of the chair is 0.076 .  Determine the mass of the chair.

Solution

Problem 47.

A man who has a mass of 100 kg, is skateboarding at 8.0 m/s when he smacks into a brick wall and comes to a dead stop in 0.4 seconds. What is his deceleration? What is force on the man due to his deceleration?

Solution

Problem 48.

A block of mass m is kept on a horizontal ruler. The friction coefficient between the ruler and the block is . The ruler is fixed at one end and the block is at a distance L from fixed end in the horizontal plane through the fixed end. What can the maximum angular speed be for which the block does not slip?

Solution

Problem 49.

If the mass of a substance is 5 grams what is its weight?

Solution

Problem 50.

An object with mass of 630 g is hung on a spring. What is the force of the object acting on the spring?

Solution

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