1. A weight lifter lifts a 490-N set of weight from the ground level to a positi
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Question
1. A weight lifter lifts a 490-N set of weight from the ground level to a position over his head, a vertical
distance of 2.00 m. How much work does the weight lifter do, assuming he moves the weights at a
constant speed (no acceleration)?
9. A mechanic pushes a 2,500 kg car from rest to a speed of v, doing 5,000 J of work in the process.
During this time, the car moves 25.0 m. Neglecting friction between car and road, find (a) v and (b) the
horizontal force exerted on the car.
19. Find the height from which you would have to drop a ball so that it would have a speed of 9.0 m/s
just before it hits the ground.25. A daredevil on a motorcycle leaves the end of a ramp with a speed of 35.0 m/s as in Figure P5.25. If
hi speed is 33.0 m/s when he reaches the peak of the path, what is his maximum height that he reaches?
Ignore friction and air resistance.
59. A force acting on a particle varies as in Figure P5.59. Find the work done by the force as the particle
moves (a) from x = 0 to x = 8.00 m, (b) from x = 8.00 m to x = 10.0 m, and (c) from x = 0 to x = 10.0 m.
60. An object of mass 3.00 kg is subject to a force of Fx that varies with position as shown in Figure
P5.60. Find the work done by the force on the object as it moves (a) from x = 0 to x = 5.00 m, (b) from x =
5.00 m to x = 10.0 m, and (c) from x = 10.0 to x = 15.0 m. (d) If the object has a speed of 0.500 m/s at x =
0, find its speed at x = 5.00 m and its speed at x = 15.0 m.64. A boy starts from rest and slides down a frictionless slide as in Figure P5.64. The bottom of the of the
slide is height h above the ground. The boy then leaves the slide horizontally, striking the ground a
distance of d from the end of the slide. Using energy methods, determine the initial height H of the boy
as a function of h and d.
66. A 2.0 m long pendulum is released from rest when the support string is at an angle of 25 with the
vertical. What is the speed of the bob at the bottom of the swing.
71. Two objects are connected by a light string passing a light frictionless pulley as in Figure P5.71. The
5.00 kg object is released at a point 4.00 m above the floor. (a) Determine the speed of each of the
objects as they pass each other. (b) Determine the speed of each object at the moment the 5.00 kg
object hits the floor. (c) How much higher does the 3.00 kg object travel after 5.00 kg object hits the
floor?
72. Two blocks, A and B (with mass 50 kg and 100 kg, respectively), are connected by a string, as shown
in Figure P5.72. The pulley is frictionless and of negligible mass. The coefficient of kinetic friction
between block A and the incline is
Explanation / Answer
19)
Givens:
v1 = 0
v2 = 9 m/s
a = 9.81 m/s2
Find d:
Use this formula
v22 = v12 +2gd
Isolate for d
d = (v22 - v12) / (2g)
= (92 - 0) / (2*9.81)
= 4.13 m
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