answer the problems using GRESA method:
1. A 53kg skateboarder pushes on the ground with -351N of force to set himself moving. How fast will the skateboarder accelerate?
2. A responsible driver, driving at a rate of 15m/s, sees the traffic light red. She presses on the brakes and after 3.20s, comes to a stop. The mass is 5400 g. How much force was exerted on the car?
1) Given:
"m=53\\ kg, F=351\\ N."
Required:
Acceleration of the skateboarder.
Equation:
"F=ma."
Solution:
"a=\\dfrac{F}{m}=\\dfrac{351\\ N}{53\\ kg}=6.62\\ \\dfrac{m}{s^2}."
Answer:
"a=6.62\\ \\dfrac{m}{s^2}."
2) Given:
"v_i=3.2\\ \\dfrac{m}{s}, v_f=0, t=3.2\\ s, m=5.4\\ kg."
Required:
Force exerted on the car.
Equation:
"F\\Delta t=m(v_f-v_i)."
Solution:
"F=\\dfrac{m(v_f-v_i)}{\\Delta t},""F=\\dfrac{5.4\\ kg\\cdot(0-15\\ \\dfrac{m}{s})}{3.2\\ s}=-25.31\\ N."Answer:
"F=-25.31\\ N."
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