You are lying in bed and want to shut your bedroom door. you have a bouncy "superball" and a blob of clay, both with the same mass. which one would be more effective to throw at your door to close it?

a. the superball.
b. neither will work.
c. the blob of clay.
d. both the same.

Choice A. The bouncy "superball" will exert approximately twice as much force than the blob of clay when tossed out at the same speed.

Explanation:

The momentum of an object is equal to the product of its mass and its velocity. The momentum of the system is conserved even if the collision is inelastic.

When the bouncy ball or the blob of clay hits the door, their momentum changes. Since momentum is conserved, the door would move in the opposite direction such that the total momentum stays at zero.

Let the mass of each object be . Suppose that both objects hit the door at a speed of in the same direction.

By Newton's Second Law, the net force on the door is proportion to the rate of change in its momentum. Assume that the two objects are in contact with the door for the same amount of time, the bouncy ball would exert about twice as much force on the door as the clay would. Hence it is "more effective" for closing the door.

what is the speed of a softball that travels 20m in 2secs

speed = 20/2 = 10 m/s

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