Two metal balls are the same size but one weighs twice as much at the other The
ID: 1612676 • Letter: T
Question
Two metal balls are the same size but one weighs twice as much at the other The balls are dropped from the roof of a single story building at the same instant of time The time it takes the balls to reach the ground below will be: (A) about half as long for the heavier ball as for the lighter one (B) about half as long for the lighter ball as for the heavier one (C) about the same for both balls (D) considerably less for the heavier ball, but not necessarily half as long (E) considerably less for the lighter ball, but not necessarily half as long The two metal balls of the previous problem roll off a horizontal table with the same speed In this situation (A) both balls hit the floor at approximately the same horizontal distance from the base of the table (B) the heavier ball hits the floor at about half the horizontal distance from the base of the table than does the lighter ball (C) the lighter ball hits the floor at about half the horizontal distance from the base of the table than does the heavier ball (D) the heavier ball hits the floor considerably closer to the base of the table than the lighter ball, but not necessarily at half the horizontal distance (E) the lighter ball hits the floor considerably closer to the base of the table than the heavier ball, but not necessarily at half the horizontal distance. A stone dropped from the roof of a single story building to the surface of the earth (A) reaches a maximum speed quite soon after release and then falls at a constant speed thereafter. (B) speeds up as it falls because the gravitational attraction gets considerably stronger as the stone gets closer to the earth (C) speeds up because of an almost constant force of gravity acting upon it. (D) falls because of the natural tendency of all objects to rest on the surface of the earth (E) falls because of the combined effects of the force of gravity pushing it downward and the force of the air pushing it downward A large truck collides head-on with a small compact car During the collision: (A) the truck exerts a greater amount of force on the car than the car exerts on the truck (B) the car exerts a greater amount of force on the truck than the truck exerts on the car (C) neither exerts a force on the other, the car gets smashed simply because it gets in the way of the truck. (D) the truck exerts a force on the car but the car does not exert a force on the truck (E) the truck exerts the same amount of force on the car as the car exerts on the truck.Explanation / Answer
1)
Ignoring buoyancy forces and friction forces , the time taken by an object dropped from a height 'h' to reach the ground is V = sqrt(2gh)
Hence both the balls take almost same amount of time
2) the horizontal displacement is given by S = horizontal velocity * time
since horizontal velocity and time is same for both the balls , they have the same value of horizontal range.
3)
similar to the problem 1, ignoring forces of air , a constant force of gravity acts on the ball and hence it's speeds up.
4) During collision of two objects, since no external force is present on the two object system, the momentum lost by one object in any amount of time must be same as the momentum gained by the second object on the same amount of time. rate of change of momentum is Force, also, according to Newton's third law if an object exerts an amount of force on a different object , the second object would exert the same magnitude of force but in opposite direction on the first object. Hence , the choice E
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