The expected speed is v = 85.5 km/h v = 85.5 km/h = (85.5 km/h)*(0.2778 (m/s)/(km/h)) = 23.75 m/s
If there is an uncertainty of 2 meters in measuring the position, then within a 1-second time interval: The lower measurement for the speed is v₁ = 21.75 m/s, The upper measurement for the speed is v₂ = 25.75 m/s. The range of variation is Δv = v₂ - v₁ = 4 m/s
The uncertainty in measuring the speed is Δv/v = 4/23.75 = 0.1684 = 16.84%
The sand provides a rough surface on top of the ice for the cars' tires to grip onto. It provides more friction. Salt melts the ice and often provides more friction (the disadvantage is that it eats concrete!).
The question ask to predict the effect where as coal can be used to generate hydrogen gas by this endothermic reason and the best answer among your choices based on the element you give is letter C. raising the temperature of the reaction mixture. I hope my answer is correct
