loop. c) (5 pts) Calculate the work done by friction on Bart as he skated down t

Question

loop. c) (5 pts) Calculate the work done by friction on Bart as he skated down the ramp and to the top of the loop. 15. A tennis ball with a mass of 55 g has an initial speed of 44 m/s. A tennis racket exerts a force on a tennis ball as shown in the graph on the right (note: time is in ms), reversing the direction of the tennis ball. a) (4 pts) Find the impulse given to the tennis ball. b) (3 pts) Find the average force exerted on the tennis ball by the racket. c) (4 pts) Find the final speed of the tennis ball 16. Two blocks are connected by a string that passes over a frictionless pulley as shown in the diagram below. Block m2 = 3.00 kg is on a plane at an angle of theta = 35 degree and block m1 = 5.00 kg hangs vertically from the string without touching the side of the incline. The coefficient of friction between the incline and m2 is 0.18. a) (6 pts) Calculate the work done by friction as m2 slides 60 cm up the incline. b) (6 pts) Calculate the speed of m1 after it has dropped 60 cm.

Explanation / Answer

15. a) impulse = F x delta T

so area under F vs time curve will give impulse :

Impulse = area = 2 (4x 1 x 10-3 /2 ) + ( 4 x 2 x 10-3 ) = 12 x 10-3 N.s

b) impulse = F x time

12 x 10-3 = F x (5-1) x 10-3

F =3 N

c) impulse = change in momentum = 0.055 ( vf - 44) = 12 x 10-3

Vf =44.22 m/s

16 . friction f =u.N = 0.18 x 3 x 9.8 x cos35 = 4.33 N

work done = F.d = - 4.33 x 0.60 = - 2.6 J

b) work done = change in K.E.

-2.6 - 3gsin35 x 0.6 + 5g x 0.60 = (3+5)v^2 /2

v =2.04 m/s

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