كرة نصف قطرها 1.7 سم ، فتكون مساحتها هي ........( علما بأن مساحة الكرة تساوي 4πr² )
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2.1 x 10¯⁵ m²
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9.1 x 10¯⁴ m²
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3.6 x 10¯ᵌ m²
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0.11 m²
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13-The graph below represents the motion of a car in two successive stages AB and BC. In which stage the resultant force acting on the car does not equal zero?
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a) AB
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b) BC
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c) AC
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d) No correct answer
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12-A car of mass 1200 kg is moving with a velocity 20 m/s .If the driver used the brakes and the speed of the car decreased to 8 m/s within 6 sec , then the average force acting on the car during this period and its direction is ……………..
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a) 2400 N in the same direction.
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b) 2400 N in the opposite direction.
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c) 1200 N in the same direction.
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d) 1200 N in the opposite direction.
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11-If there are two persons falling from different heights , the person who falls from the largest height will be harmed more than the other , and this is due to……………
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a) Increasing the time of impact
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b) Decreasing the time of impact
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c) Increasing the change in the velocity
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d) Increasing air resistance
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10-The collision of a large truck with a wall is more destructive than the collision of a small car although they have the same velocity , that is due to in case of small car …………..
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a)by increasing mass the force of collision will increase.
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b) by increasing time of impact the force of collision will decrease.
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c) by decreasing mass the force of collision will decrease.
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d) by increasing acceleration the force of collision will increase.
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9-If a person falls from a height in water he will not be harmed while if he falls on the ground he will be harmed , because in case of falling in water …………………..
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a)Time of impact increase
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b)Time of impact decreases
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c)Velocity increases
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d)Velocity decreases
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7-If the force acting on a body is doubled while its mass is decreased to its half , acceleration of its motion……………….