79. An airplane pilot fell 370 m after jumping from an aircraft without his parachute opening. He landed in a snowbank, creating a crater 1.1 m deep, but survived with only minor injuries. Assuming the pilot's mass was 88 kg and his speed at impact was 45 m/s, estimate: (a) the work done by the snow in bringing him to rest: (b) the average force exerted on him by the snow to stop him; and (c) the work done on him by air resistance as he fell. Model him as a particle.

ry the system T Am 27. A 5000 kg dump truck has a maximum 400 hp (1 hp = 746 W), and it is moving up on an inclined road with a slope of 15 degrees. If the frictional coefficient on the road is 0.80, what is the max constant speed that the trucker can maintain on the inclined? FV FN fi FL trictional No motion. (0) FNA Force F is now even 6.1 (a) The forces on a Friction An external ntronger but is still 12

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As a simple pendulum swings back and forth, the forces acting on the suspended object are the gravitational force, the tension in the supporting cord, and air resistance. (i) Which of these forces, if any, does no work on the pendulum at any time? (Select all that apply.) 1)gravitational force 2)tension in the supporting cord 3)air resistance (ii) Which of these forces does negative work at all times during its motion? (Select all that apply.) 1)gravitational force 2)tension in the supporting cord 3)air resistance

(a) If force and displacement have the same direction, the work done is ________________. (b) If force and displacement have opposite directions, the work done is ___________________.

Air bags are used in cars to decelerate the occupants slowly when a car is suddenly decelerated in a crash. (a) Compute the work done by the decelerating force acting on a 55.0 kg driver if the car is brought to rest from an initial speed of 20.0 m/s. (b) Find the minimum thickness of the air bag if the average decelerating force is not to exceed 8900 N (2000 lb), and the center of the car moves forward 0.800 m during impact

(a) A 75-kg man steps out a window and falls (from rest) 1.0 m to a sidewalk. What is his speed just before his feet strike the pavement? (b) If the man falls with his knees and ankles locked, the only cushion for his fall is an approximately 0.50-cm give in the pads of his feet. Calculate the average force exerted on him by the ground during this 0.50 cm of travel. This average force is sufficient to cause damage to cartilage in the joints or to break bones.

Using energy considerations, calculate the average force (in N) a 69.0 kg sprinter exerts backward on the track to accelerate from 2.00 to 6.00 m/s in a distance of 25.0 m, if he encounters a headwind that exerts an average force of 30.0 N against him. (Enter a number.)

(1.) An 18 kg crate slides up a 32.0° slope (inclined plane) that is 25 m in length and has a kinetic friction coefficient of 0.36. The crate is given an initial upward speed of 21 m/s as it starts up from the bottom of the slope. Applying the principle of the conservation of mechanical energy in the presence of dissipative forces (friction), determine its final speed as it reaches the top of the slope.

A crate of mass 9.0 kg is pulled up a rough incline with an initial speed of 1.42 m/s. The pulling force is 110 N parallel to the incline, which makes an angle of 20.6° with the horizontal. The coefficient of kinetic friction is 0.400, and the crate is pulled 4.92 m. (a) How much work is done by the gravitational force on the crate? |-152.68 (b) Determine the increase in internal energy of the crate-incline system owing to friction. 33.02 A careful free-body diagram of the crate may help you determine the magnitude of the friction force. J (c) How much work is done by the 110-N force on the crate? 541.2 (d) What is the change in kinetic energy of the crate? 355.5 You appear to have calculated the change in kinetic energy correctly using your incorrect results from the previous parts. J (e) What is the speed of the crate after being pulled 4.92 m? 9 You appear to have calculated the speed correctly using your incorrect result from part (d). m/s