A 500-N parachutist opens his chute and experiences an air resistance force of 8

Question

A 500-N parachutist opens his chute and experiences an air resistance force of 800 N. The net force on the parachutist is then. A) 500 N downward. B) 800 N downward. C) 500 N upward. D) 300 N upward. E) 300 N downward. A golf hall is thrown at and bounces backward from a massive bowling ball that is initially at rest. After the collision. compared to the golf ball, the bowling ball has more A) momentum and more kinetic energy. B) kinetic energy, but less momentum. C) momentum, but leas kinetic energy. D) need more information Strictly speaking, to weigh less in the Northern Hemisphere you should move to a location farther A) east. B) south (toward the equator). C) west. D) north (toward the pole). A block of ice sliding down an incline has half its maximum kinetic energy A) at the bottom. B) halfway down. C) at the top. D) need more information When you drop a rubber ball on the floor it bounces back. The force exerted on the ball to produce bouncing is by the A) ball. B) floor. C) need more information Two billiard balls having the same mass and speed roll toward each other. What is their combined momentum after they meet? A) zero B) twice the sum of their original momentums C) half the sum of their original momentums D) need more information The circumference of a bicycle wheel is 2 meters. If it rotates at 1 revolution per second then its linear speed is A) 1 m/s. B) 3 m/s. C)2m/s. D) 3.14 m/s. E) 6.28 m/s. A pair of wires support a heavy pointing. Tension in the wires is greater when they are A) not vertical. B) the same regardless of the wire orientation. C) vertical. D) none of the above If vertically falling rain makes slanted 45 degree streaks on the side windows of a moving car, the speed of the car A) exceeds the speed of the falling drops. B) equals the speed of the falling drops. C) is less than the speed of the falling drops. D) need more information

Explanation / Answer

9) The net force acting on an object is the sum total of all the force vectors acting on it . Since force is a vector quantity the direction is also to be accounted for.

So the forces here are
500 N down ( lets denote a negative sign for down) = -500 N

After the parachute, resistance force = 800 N up= +800 N

so total force = +800 -500 = +300 N or 300 N upwards

10) The momentum and kinetic energy of an object are dependent on the mass and velocity of the objects. While both the terms here are defined, but the individual values and the type of collision are not mentioned. so we cannot say and compare the energies for sure. So we need more information.

11 ) Weight is the product of mass with the g value, which is inversely proportional to the radius of the earth.
since the earth bulges, the g value at the equator is less than that on poles, and so you must move towards the equator to weigh less.

12 ) the kinetic energy is defined as (1/2)(m)(V2)

and by an equation of motion, we know that V2-U2= 2*a*s

so, assuming initial velocity = zero, we get
KE = (1/2) ( m ) (2*a*s)

since acceleration is constant on the incline, the KE halfway the incline is (1/2) times the maximum KE

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