Ch 09: Work and Kinetic Energy

Knight Calc - Physics for Scientists and Engineers 5th Edition

Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796당신이 사용하는 게 아니라요?교과서 변경

Knight Calc 5th Edition

Ch 09: Work and Kinetic Energy

문제 36b

9장, 문제 36b

How much work must you do to push a 10 kg block of steel across a steel table at a steady speed of 1.0m/s for 3.0 s? What is your power output while doing so?

검증된 단계별 안내

Step 1: Identify the forces acting on the block. Since the block is moving at a steady speed, the net force is zero. The force you apply must balance the kinetic friction force. The formula for the force of kinetic friction is:

f

_k = μ_kmg, where

μ

_k is the coefficient of kinetic friction,

m

is the mass of the block, and

g

is the acceleration due to gravity.

Step 2: Determine the coefficient of kinetic friction for steel on steel. From standard tables, the coefficient of kinetic friction

μ

_k for steel on steel is approximately 0.6. Use this value in the formula for the frictional force.

Step 3: Calculate the work done. Work is given by the formula:

W = f

_kd, where

d

is the distance the block is pushed. To find

d

, use the relationship

d = v t

, where

v

is the speed (1.0 m/s) and

t

is the time (3.0 s).

Step 4: Calculate the power output. Power is the rate at which work is done and is given by the formula:

P = W / t

, where

W

is the work done and

t

is the time (3.0 s).

Step 5: Substitute the known values into the formulas to compute the work done and the power output. Ensure all units are consistent (e.g., mass in kilograms, distance in meters, time in seconds).

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

영상 길이:

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Work

Work is defined as the product of force and displacement in the direction of the force. In physics, it is calculated using the formula W = F × d, where W is work, F is the force applied, and d is the distance moved. When pushing an object at a constant speed, the work done is equal to the force of friction multiplied by the distance traveled.

Friction

Friction is the resistive force that opposes the motion of an object when it is in contact with another surface. It is influenced by the nature of the surfaces in contact and the normal force acting between them. For a block sliding on a table, the frictional force can be calculated using the coefficient of friction and the weight of the block.

Power

Power is the rate at which work is done or energy is transferred over time. It is calculated using the formula P = W/t, where P is power, W is work, and t is the time taken. In this scenario, once the work done to push the block is determined, the power output can be calculated by dividing the work by the time taken to push the block.