Two metal balls are the same size but one weights twice as much as the other. Th

Question

Two metal balls are the same size but one weights twice as much as the other. The balls are dropped from the roof of single story building at the same instant of time. The time it takes the balls to reach the ground below will be About half as long for the heavier ball as for the lighter one. About half as long for the lighter ball as for the heavier one. About the same for both balls Considerable less for the heavier ball, but not necessarily half as long Considerable less for the lighter ball, but not necessarily half as long. A large truck collides head-on with a small compact car. During the collision: The truck exerts a greater amount of force on the car than the car exerts on the truck. The car exerts a greater amount of force on the truck than the truck exerts on the car Neither exerts a force on the other, the car get smashed simply because it gets in the way of the truck The truck exerts a force on the car but the car does truck The truck exerts the same amount of force on the car as the car exerts on the truck. A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is less than its weight. more than its weight. equal to its weight. A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is zero less than 30 m/s but larger than zero. about 30 m/s. d. more than 30 m/s. More information is needed for an estimate. Inside a freely falling elevator, there would be no apparent weight for you. gravitational force on you. both of these none of these

Explanation / Answer

1) Answer:C

From Newton’s second law of motion,F=ma so that a=F/m

The force between the two objects is directly proportional to the product of the masses and inversely proportional to the square of the distance between them.

The heavier ball has twice the force and twice the mass so the acceleration would be the same.

Two balls dropped simultaneously from the same height having the same acceleration should hit the ground at the same time....

From Newton’s third law of motion, we know that every action has an equal and opposite reaction.

Impulse is force multiplied by time, and time of contact is the same for both, so the impulse is the same in magnitude for the two trucks. Change in momentum is equal to impulse, so changes in momenta are equal. With equal change in momentum and smaller mass, the change in velocity is larger for the smaller truck. Since acceleration is change in velocity over change in time, the acceleration is greater for the smaller truck.

3) Answer:C

A rock is thrown vertically into air. At the top of its trajectory its acceleration is equal to acceleration due to gravity, g = 9.8 m/s2

Hence Force acting on it = mg = weight

4) If there is no air resistance, then the package will only be affected by gravity.

If the truck is moving at 30m/s, then so is the package when it leaves the truck.

Since their is no resistance to slow the package down, it will fall vertically at 32 feet per second per second while continuing to travel horizontally at 30 m/s. It will continue to move horizontally at 30 m/s until it hits the ground when friction comes into play.

Since none of the answers is "exactly 30 m/s" than b and c are correct. "a" and "d" cannot be correct. "b,c and d" ARE estimates so "e" can't be correct.

Actually, none of the answers are correct because the correct answer would be "exactly 30 m/s".

5) Answer: A

The lift falls freely under gravity. The man also falls freely under gravity. Both move down with an acceleration g. For the man there is no up ward force to prevent his fall. Or the apparent weight is zero. The man feels that he has lost all his weight.

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