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Andrew skis down a hill - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1
Question 2
Andrew skis down a hill. (a) Andrew starts from the top of the hill and his speed increases as he goes downhill. He controls his speed and direction by using his s... show full transcript
Worked Solution & Example Answer:Andrew skis down a hill - Edexcel - GCSE Physics - Question 2 - 2013 - Paper 1
Step 1
Describe the energy changes that happen between starting and stopping.
Answer
When Andrew starts skiing from the top of the hill, he possesses gravitational potential energy (GPE) due to his height. As he descends, this potential energy is converted into kinetic energy (KE), increasing his speed. During the descent, some energy is also converted into thermal energy due to air resistance and friction, which generates heat. Upon coming to a stop at the bottom of the hill, the kinetic energy is dissipated as heat and sound energy, which is transferred to his surroundings.
Step 2
Step 3
Calculate the average force on Andrew as he slows down.
Answer
To find the average force (F), we use the formula:
F = rac{ ext{change in momentum}}{ ext{time}}
Given:
- Initial momentum = 2000 kg m/s
- Final momentum = 0 kg m/s (after coming to a stop)
- Time taken = 2.3 s
The change in momentum = 2000 kg m/s. Hence,
F = rac{2000 ext{ kg m/s}}{2.3 ext{ s}} = 869.6 ext{ N}
So, the average force is approximately 870 N.
Step 4
Use ideas about force and momentum to explain why he is not injured.
Answer
Andrew is not injured because the force acting on him when he falls is relatively small. The impact time when he hits the ground is quite long, allowing the force to be spread out over time. Moreover, the acceleration during the fall is not very large, since the distance of impact is small, which leads to a gradual change in his momentum rather than an abrupt stop, minimizing injury risk.