A crane is lifting a heavy block from the ground to the top of a building - Edexcel - GCSE Physics - Question 4 - 2012 - Paper 1
Question 4
A crane is lifting a heavy block from the ground to the top of a building.
This is the velocity/time graph for the block as it travels upwards.
(i) For how many se... show full transcript
Worked Solution & Example Answer:A crane is lifting a heavy block from the ground to the top of a building - Edexcel - GCSE Physics - Question 4 - 2012 - Paper 1
Step 1
For how many seconds is the block moving at a constant velocity?
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Answer
The block is moving at a constant velocity for 16 seconds. This can be observed from the velocity/time graph where the velocity remains steady at 5 m/s during this time.
Step 2
Draw an arrow on the diagram to represent the weight of the block.
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Answer
A downward arrow should be drawn starting from the center of the block, indicating the force of gravity acting on it.
Step 3
Complete the sentence by putting a cross (✗) in the box next to your answer.
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Answer
The correct answer is D zero. When the block moves upwards at a constant velocity, the upward and downward forces are balanced, resulting in a net force of zero.
Step 4
Use the velocity/time graph to calculate the acceleration of the block during the first 2 s.
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Answer
To calculate acceleration, we use the formula:
a=ΔtΔv
During the first 2 seconds, the velocity changes from 0 m/s to 5 m/s. Therefore,
a=2−05−0=25=2.5 m/s2
The unit of acceleration is m/s².
Step 5
Explain why the upward force from the cable during the first 2 s is greater than the upward force for the next 4 s.
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Answer
During the first 2 seconds, the block is accelerating from rest to a constant speed of 5 m/s. Therefore, the upward force from the cable must not only overcome the weight of the block but also provide the additional force necessary for acceleration. After the first 2 seconds, the block moves at a constant speed, and the forces are balanced, so the upward force equals the weight of the block.
Step 6
Explain how the graph shows that the second crane has a larger power.
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Answer
The second crane's velocity/time graph shows a steeper incline and reaches the same height faster than the first crane's graph. Power is defined as the rate of doing work or the amount of energy transferred over time. Therefore, since the second crane achieves the desired height in a shorter time, it indicates a greater power output.
