o children push on opposite sides of a door during play. Both push horizontally and perpendicular to the door. One child pushes with a force of 165 N at a distance of 0.600 m from the hinges

1

Two children push on opposite sides of a door during play. Both push horizontally and perpendicular to the door. One child pushes with a force of 165 N at a distance of 0.600 m from the hinges, and the second pushes at a distance of 0.450 m. What force must the second exert to keep the door from moving? Assume friction is negligible.
 N

2.

Suppose a horse leans against a wall as in Figure 5.35. Calculate the force exerted on the wall assuming that force is horizontal and using the data in the schematic representation of the situation. Note that the force exerted on the wall is equal and opposite to the force exerted on the horse, keeping it in equilibrium. The total mass of the horse and rider is 525kg. Take the data to be accurate to three digits.
 N

Figure 5.35

3.

A sandwich board advertising sign is constructed as shown in Figure 5.39. Its mass is 8.80 kg.

Figure 5.39

• Calculate the tension in the chain assuming no friction between the legs and the sidewalk.
   N
  (b) What force is exerted by each side on the hinge?
   N (acting horizontally)

4.

Suppose you use an ideal pulley of the type shown in Figure 5.18(a) to support a car engine of mass 115 kg.

Figure 5.18

• What would the tension in the rope be?
   N
  (b) What force must the ceiling supply, assuming you pull straight down on the rope? Neglect the pulley system’s mass.
   N (upward)

5.

Suppose you use an ideal pulley of the type shown in Figure 5.18(c) to support a car engine of mass 135 kg.

Figure 5.18

• What would the tension in the rope be?
   N
  (b) What force must the ceiling supply, assuming you pull straight up on the rope? The pulley system’s mass is7.50 kg.
   N (upward)

6

The upper leg muscle (quadriceps) exerts a force of 1330 N, which is carried by a tendon over the kneecap (the patella) at the angles shown in Figure 5.43. Find the magnitude and direction of the force exerted by the kneecap on the upper leg bone (the femur).
 N
 ° (counter-clockwise from an axis directed to the left)

Figure 5.43

7.

Suppose you use an ideal pulley of the type shown in Figure 5.18(b) and find it necessary to exert a force of 370 N to support a load.

Figure 5.18

(a) What is the load’s mass?
 kg
(b) What force is exerted on the ceiling? Neglect the pulley system’s mass.
 N (upward)