A mechanical jack is used to lift a car.(i) (1 mark)If a 1300 kg car is raised 0.28 m, how much work was done on the car?(ii) (1 mark)If the lever was pushed a total distance of 5.1 m at constant force, how large was the force applied? Assume 100% efficiency.(iii) (3 marks)Now suppose the jack is only 60% efficient. The person operating the jack supplies 75 W of power. How long does it take to lift the car the 0.28 m distance?
Question
A mechanical jack is used to lift a car.(i) (1 mark)If a 1300 kg car is raised 0.28 m, how much work was done on the car?(ii) (1 mark)If the lever was pushed a total distance of 5.1 m at constant force, how large was the force applied? Assume 100% efficiency.(iii) (3 marks)Now suppose the jack is only 60% efficient. The person operating the jack supplies 75 W of power. How long does it take to lift the car the 0.28 m distance?
Solution
(i) Work is calculated by the formula W = mgh, where m is the mass, g is the acceleration due to gravity (9.8 m/s^2 on Earth), and h is the height.
So, W = 1300 kg * 9.8 m/s^2 * 0.28 m = 3556.8 Joules.
(ii) Work is also calculated by the formula W = F*d, where F is the force and d is the distance. We can rearrange this formula to solve for force: F = W/d.
So, F = 3556.8 Joules / 5.1 m = 697.41 Newtons.
(iii) If the jack is only 60% efficient, then the actual work done is only 60% of the work supplied. So, the work done is 0.60 * 3556.8 Joules = 2134.08 Joules.
Power is work done per unit time, or P = W/t. We can rearrange this to solve for time: t = W/P.
So, t = 2134.08 Joules / 75 Watts = 28.45 seconds.
Similar Questions
In 1990, Walter Arfeuille of Belgium lifted a 281.5kg object through a distance of 17.1cm using only his teeth.(a) How much work was done on the object by Arfeuille in this lift, assuming the objectwas lifted at constant speed?(b) What total force was exerted on Arfeuille’s teeth during the lift?
A weightlifter lifts a weight of 500N from the ground over her head, a distance of 1.8m. How much work has been done to move the weight?
A tow truck attaches a cable to a car stuck in a muddy ditch. The 1250 kg car is pulled upan embankment to a height of 1.8 m at a constant speed. The cable exerts a force of 5500 Nover a distance of 12.6 m to pull the car out of the ditch. K/u T/I(a) What is the amount of useful energy produced? [ans: 22 kJ](b) What amount of energy is used to pull the car from the ditch? [ans: 69 kJ](c) Calculate the percent efficiency. Why is the efficiency less than 100 %? [ans: 32 %]
A crane lifts a 432-kg steel beam vertically a distance of 62.8 m.How much work does the crane do on the beam if the beam accelerates upward at 2.5 m/s2?Neglect frictional forces, and express your answer in joules.
A student uses a machine to lift a 500N weight vertically a distance of 3 meters in 5 seconds. What is the power output, assuming that no other external factors are acting during the lift?
Upgrade your grade with Knowee
Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.