A sled of mass is moving on frictionless ice with an initial speed of

PHYSICS · Subjective · CBSE · Physics · Work, Energy and Power · Work, Energy and Power

Problem

A sled of mass

10\,\text{kg}

is moving on frictionless ice with an initial speed of

5\,\text{m\,s}^{-1}

. A small rocket motor fixed to the sled provides a constant thrust whose useful mechanical power output is

40\,\text{W}

. (a) Show that the speed

v

of the sled at any instant

t

after the motor is ignited satisfies the relation

v^{2}=v_{0}^{2}+\dfrac{2P}{m}t

, where

v_{0}

is the initial speed and

P

is the constant power. (b) Using the result of part (a), determine the time required for the sled to double its initial speed. (c) Find the sled's acceleration at the instant when its speed reaches

10\,\text{m\,s}^{-1}

Related theory

Kinetic Energy
Power
Work, energy and power

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