godssent2 Posted May 14, 2014 Share Posted May 14, 2014 Im struggeling on this question. please help if possible, would love an explanation! 1. During a sprint start, a 69.8 kg athlete exerts constant horizontal and vertical forces of 955 N and 987 N respectively, against the starting blocks. This resulted in a change in horizontal velocity of 7.94m.s-1. Calculate the time over which the horizontal force was applied to the start blocks. Quote Link to comment Share on other sites More sharing options...
A lazy Cat Posted May 14, 2014 Share Posted May 14, 2014 2 Quote Link to comment Share on other sites More sharing options...
godssent2 Posted May 14, 2014 Author Share Posted May 14, 2014 2 Helpfull replies would be appreciated... 1 Quote Link to comment Share on other sites More sharing options...
Theodore Bagwell Posted May 14, 2014 Share Posted May 14, 2014 (edited) Im struggeling on this question. please help if possible, would love an explanation! 1. During a sprint start, a 69.8 kg athlete exerts constant horizontal and vertical forces of 955 N and 987 N respectively, against the starting blocks. This resulted in a change in horizontal velocity of 7.94m.s-1. Calculate the time over which the horizontal force was applied to the start blocks. Hmm, so if i'm right the athlete accelerates at the first starting position with given forces? This is what i would say: F(total) = F(horizontal) + F(vertical) = 987 + 955 = 1942N A = F/m = 1942 / 96,8 = 20m.s-2 So his acceleration is 20m.s-2 Now i stuck as theres no distance given (so it's not possible to calculate the time). Maybe it helped, maybe not Edited May 14, 2014 by Matrix Quote Link to comment Share on other sites More sharing options...
Dard Posted May 14, 2014 Share Posted May 14, 2014 Hmm, so if i'm right the athlete accelerates at the first starting position with given forces? This is what i would say: F(total) = F(horizontal) + F(vertical) = 987 + 955 = 1942N A = F/m = 1942 / 96,8 = 20m.s-2 So his acceleration is 20m.s-2 Now i stuck as theres no distance given (so it's not possible to calculate the time). Maybe it helped, maybe not Nice Japanese skills, I have no idea what the heck you're talking about xD 2 Quote Link to comment Share on other sites More sharing options...
tes1234 Posted May 14, 2014 Share Posted May 14, 2014 By conservation of linear momentum; Initial momentum = 0, final momentum = 69.8 x 7.94 kgms^-1. Impulse due to horizontal force causes change in (horizontal) linear momentum - impulse = force x time, so we have 955 * t = dp. Solve for t. Quote Link to comment Share on other sites More sharing options...
godssent2 Posted May 14, 2014 Author Share Posted May 14, 2014 Cheers guys your responses are appreciated. Quote Link to comment Share on other sites More sharing options...
