Question

please help with 8.5, 8.6, 8.7, 8.8

work done by gravity positive, negative, or zero (c) After the block reaches the bottom, and continues sliding back up the bowl until it comes to rest, is the additional work done by gravity positive, negative, or zero? (d) It the bowl is ot frictionless, will the block slide back up to the same height it (c) When friction is present, and after the block reaches the bottom, is the additional was released from on the opposite side of the bowl? work done by friction as the block continues sliding from the bottom to the max 8.6 A 180 g fedora is released from rest from the top of a frictionless circus slide oriented (c) wil?'I İH L]ic? H(Kxal or the fedora at 1.hc IKI.10111 or 1.hc slide.? Answer: (a) 3.87 J (b) 3.87 J (c) 6.53 m/s 32 PHYS 131 8 POTENTIAL ENERGY 8.7 A 180 g feciora is given an initial speed of 9.00 /s up a slice that is oriented at 26.0 above the horizontal. (a) the surface was fictionless, what would you predict as the increase in vertical position (height of the fedora? (b) There is friction between the fedora and the slide. If the actual vertical position height) of the hat increases by only 2.50 m before coming to rest, what is the work done by friction? Answer: (a) 4.13 m (b-2.88J 8.8 A 300 g block is placed at rest against a spring with spring constant equal to 45.0 N/m which is compressed by 6.00 cm. The spring is located at the beginning of the friction less track shown below. 8.00 cm (a) What is the potential energy stored in the initially compressed spring! (b) What is the speed of the block immediately after being launched by the spring before the block goes down)? (c) What is the speed of the block at the bottom of the track? (d) What is the maximum distance above the bottom of the track that the block reaches on the right vertical section of the track? Answer: (a) 8.10x102 J (b) 7.35x10-1 /s (c1.45 m/s (d) 10.8 crm

Answer 1

8.5

a) Yes, the block(and system) does not lose energy, so the block will rise to the same height.

b) The work done by gravity is positive as the gravitational potential energy of the block decreases when moves down to the bottom, since the work done by the gravity = - change in potential energy ,

Work done by gravity is positive.

c) The work done by gravity is negative this time. The potential energy of the block increases as it rises to the maximum height.

d) No, the block will not rise to the same height. The block loses energy due to friction.

e) The work done by the friction is negative as the block does not rise to the same height.

86 a) The itial otal mechanical enerax of the mechanical eners edora Ko a Fedora starts sfarts al hest nm d sn (26) 26.0 he d sin26)

b) The final total mechanical enegy 3-87J as no energy is kost CI

at the boton, kf=Lmy2 -speed at thebottom 2 vニ6.ssa-l The.pe ed