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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 initially possesses gravitational potential energy (GPE) due to his height above the ground. As he descends, this potential energy is converted into kinetic energy (KE), resulting in an increase in his speed.
As he nears the bottom of the hill, some of the energy is transformed into heat due to air resistance and friction between the skis and the snow. Once he comes to a stop, the remaining kinetic energy is dissipated as heat and sound energy, as well as being transferred to the surroundings.
Step 2
Step 3
Calculate the average force on Andrew as he slows down.
Answer
To calculate the average force, we use the formula:
F = rac{ ext{Change in momentum}}{ ext{Time}}
Here, the initial momentum is 2000 kg m/s and it reduces to 0 kg m/s. Therefore, the change in momentum is:
Time taken to stop is 2.3 s. Thus, the average force is:
F = rac{2000}{2.3} \\ \\ \\ = 869.57 ext{ N} \\ = 870 ext{ N}
Step 4
Use ideas about force and momentum to explain why he is not injured.
Answer
When Andrew falls, the force acting on him is spread out over a longer period due to the deceleration as he slides on the snow. The longer impact time reduces the average force experienced by his body.
Additionally, the distance over which he comes to a stop further decreases the force of impact. Since the average force is lower than what would typically cause injury, he is able to avoid injury despite moving quickly.