00:01
So let's say that the position of an oscillating astronaut on a spring is given by 0 .3 meters times the sign of pi times t, where the argument of the sign is in radiance.
00:21
So we want to know, what is the force the spring exerts on the astronaut at one second? so the force, there are two ways of writing this.
00:29
So you could just write it as the astronaut's mass times a acceleration, which the mass of the astronaut is 75 kilograms.
00:39
And the acceleration at that time, so this will be 75 kilograms times, times 0 .3 meters times pi, we'll write as this pi radians per second squared, times the sign of pi, which the sign of pi is zero, if you think about it.
01:00
So this is just going to be zero.
01:05
And then part b asks, what about, what is the force at 1 .5 seconds? so now it's the same coefficient of the sign, right? it's 75 kilograms times 0 .3 meters times pi radians a second squared...