Hello- Can someone please help me with this one??? I've had someone explain it to me already (not on this forum) but for some reason i forgot how to do it!!!
Thanks in advance!!!
Sam is on his push bike riding at 4 m/s. He comes across a huge hill, with a gradient of 50 degrees, and realises his breaks don’t work. He goes speeding down the hill in a panic for and minute and two seconds, until he comes face to face with a brick wall. If he, plus his bike has a mass of 70 kg, and there was a friction force of 113N, then what was his velocity before he hit the wall?
Hey gillies! Welcome to the forums!
This is a really tough question for HSC level! But here we go
So we are considering forces along the direction of the hill. So, we need to see what component of gravity will act along the hill (picture a vector at 53 degrees to the horizontal, then another perpendicular to that forming a right angled triangle with gravity as the hypotenuse. We'll call this \(F_h\):
Now, we have a frictional force acting against this, so the total force acting down the hill:
Now this force acts for 1 minute and two seconds, starting at a velocity of 4 metres per second. We know the acceleration will be given by:
So we can use the velocity formula:
Now I
may have stuffed up some maths above (I'm procrastinating in a lecture, lol) but I get about 370 metres per second, exceeding the speed of sound. This doesn't quite seem sensible, but the question seems a little 'humorous' so maybe! If it is the answer, Sam is... Not in a good state
Does this make sense?