University Physics Al No 6 Work, Energy, and the Cwe Theorem Class Number ame I. Choose the Correct Answer 1. Which of the following quantities are independent of the choice of inertial frame?(There may be more than one correct answer) (BC) (A)Velocity B)Acceleration (C)Force (D)Work In all the inertial frame, the forces acted on a body are same F= ma=F=ma, therefore the force and acceleration are independent of the choice of inertial frame 2. The force exerted by a special compress device is given by F(x)=lx(x-1)for 0<xsl where / is the maximum possible compression and k is a constant. The force required to compress the device a distance d is a maximum when (A)d=0.(B)d=l/4.(C)d=l/√2.(D)d=1/2.(E)d=l Solution The force is F(x)=k(x=)=k(sI2 k/. when 0 or x1, The force is a maximum According to the problem, x=d-l 3. A particle has a constant kinetic energy KE. Which of the following quantities must also be constant? (A)Position (B)Speed (C)Velocity D)Momentum Solution Since the kinetic energy is KE=-my2, it is dependent of the speed 4. A020kg puck slides across a frictionless floor with a speed of 10 m/s. The net work done on the (B)-10J (C)0J (D)20J Solution Using the CWE theorem: otal=AKE, the net work done on the puck is zeroUniversity Physics AI No. 6 Work, Energy, and the CWE Theorem Class Number Name I．Choose the Correct Answer 1. Which of the following quantities are independent of the choice of inertial frame? (There may be more than one correct answer) （ BC ） (A) Velocity (B) Acceleration (C) Force (D) Work Solution： In all the inertial frame, the forces acted on a body are same, F = ma = F′ = ma′ r r r r , therefore the force and acceleration are independent of the choice of inertial frame. 2. The force exerted by a special compress device is given by F (x) kx(x l) x = − for 0 ≤ x ≤ l , where l is the maximum possible compression and k is a constant. The force required to compress the device a distance d is a maximum when （ E ） (A) d = 0 . (B) d = l / 4 . (C) d = l / 2 . (D) d = l / 2 . (E) d = l Solution: The force is 4 ) 2 ( ) ( ) ( 2 l 2 kl F x kx x l k x x = − = − − , when x=0 or x=l, The force is a maximum. According to the problem, x=d=l 3. A particle has a constant kinetic energy KE. Which of the following quantities must also be constant? （ B ） (A) Position (B) Speed (C) Velocity (D) Momentum Solution: Since the kinetic energy is 2 2 1 KE = mv , it is dependent of the speed. 4. A 0.20kg puck slides across a frictionless floor with a speed of 10 m/s. The net work done on the puck is （ C ） (A) -20J (B) -10J (C) 0J (D) 20J Solution： Using the CWE theorem: Wtotal = ∆KE , the net work done on the puck is zero