Interactive multiple-choice quiz: اختبار العلوم انسباير الصف الثامن الوحدة الثانية
اختبار تقييمي لمادة العلوم لطلبة الصف الثامن حول الوحدة الثانية. يغطي الاختبار مفاهيم الطاقة الحركية وطاقة الوضع الميكانيكية. يركز على علاقة السرعة والكتلة بالطاقة وقانون حفظ الطاقة.
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اختبار شهادة تدريبي مؤقت للصف والمادة والفصل نفسه.
اختر إجابة واحدة لكل سؤال. عند الاختيار ستظهر النتيجة فورًا: الأخضر صحيح، والأحمر خطأ، وسيظهر تفسير الإجابة مباشرة إن كان متوفرًا. وبعد آخر سؤال ستظهر الدرجة النهائية تلقائيًا.
Aiden collected canned goods for a neighborhood service project. He pulled a plastic wagon behind him to put the items in. From the time Aiden began until he finished collecting, the mass of the wagon tripled. The walk back to Aiden's house was downhill and the speed of the wagon tripled. What happened to the kinetic energy when the mass tripled? What happened to the kinetic energy when the speed tripled?
Explanation
Kinetic energy is proportional to mass ($KE \propto m$) and proportional to the square of velocity ($KE \propto v^2$). Tripling the mass triples the KE (3 ×), and tripling the speed increases KE by a factor of 32 = 9.
Question 2
2
Points: 1
The figure below shows mass and relative kinetic energy in energy bars for three vehicles. What can you determine about the speed of the blue car?
Explanation
According to the diagram, the red car and the green truck both have a speed of 15 m/s, while the blue car has a speed of 7 m/s, which is less than the truck's speed.
Question 3
3
Points: 1
What does a moving object's kinetic energy depend on?
Explanation
Kinetic energy depends on the mass of the object and its speed (velocity).
Question 4
4
Points: 1
If the mass of an object is decreased by a factor of $\frac{1}{2}$, by what factor does the kinetic energy decrease?
Explanation
Kinetic energy is directly proportional to mass ($KE = \frac{1}{2}mv^2$). If mass is halved, the kinetic energy is also halved.
Question 5
5
Points: 1
What is translational kinetic energy due to?
Explanation
Translational kinetic energy is the energy of an object moving from one location to another (change in position).
Question 6
6
Points: 1
Use the diagram below to answer the question. In the rack there is a bike helmet and a pair of roller skates. The mass of the bike helmet is 550 g and the mass of a roller skate is 2,000 g. Which item has more energy?
Explanation
Both items are at the same height (stationary on the rack), so they have gravitational potential energy (GPE = mgh). Since the roller skates have a much larger mass (2,000 g vs 550 g), they have more potential energy.
Question 7
7
Points: 1
What happens to the elastic potential energy of a spring as you change its shape more?
Explanation
Elastic potential energy increases as an object (like a spring or rubber band) is stretched or compressed further from its original shape.
Question 8
8
Points: 1
How does the position of an object relative to the center of a gravitational field affect its potential energy?
Explanation
Gravitational potential energy increases as the distance (height) between the object and the source of the gravitational field (like Earth's center) increases.
Question 9
9
Points: 1
Why does a ball fall when you let go of it above the ground?
Explanation
Gravity is the attractive force between objects with mass; Earth's gravity pulls the ball toward its center.
Question 10
10
Points: 1
Why must a roller coaster be tall enough?
Explanation
A taller height provides more gravitational potential energy, which converts into the kinetic energy (speed) required for the coaster to complete the track's loops.
Question 11
11
Points: 1
The graph shows the kinetic energy (KE) and potential energy (PE) of a bouncing ball over a period of 9 seconds. Use the graph to answer the question. When does the ball have the most kinetic energy?
Explanation
In the provided graph, the kinetic energy (KE) peaks around 2 seconds, which corresponds to the point where the ball is moving fastest just before its first bounce.
Question 12
12
Points: 1
When a basketball is tossed into the air and moves upward, what happens to its kinetic energy and potential energy?
Explanation
As the ball moves upward, it slows down (losing kinetic energy) and its height increases (gaining gravitational potential energy).
Question 13
13
Points: 1
Friction in the form of air resistance acts on pendulums. What type of energy is mechanical energy transferred into as a result?
Explanation
Friction and air resistance convert mechanical energy into thermal energy (heat).
Question 14
14
Points: 1
What does the law of conservation of energy state?
Explanation
The law of conservation of energy states that the total energy in an isolated system remains constant; it only transforms from one form to another.
Question 15
15
Points: 1
According to the text, what is the most widely used renewable energy resource?
Explanation
Hydroelectric power (energy from falling water) is traditionally the most widely used large-scale renewable energy source.
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