Question
1. A physics student does a work on a 2.5 kg curling stone by exerting 50 N of force horizontally over a distance of 2 m. Calculate the work done by the student on the curling stone. 2. Calculate the kinetic energy of the following objects. (a) A man of mass 50 kg running at a speed of 20m/s (b) A200 g of bullet fired at a speed of 300m/s (c) A car of mass 1000 kg travelling at 80 meter per second 3. Calculate (a) The potential energy of 10 kg stone placed at a height of 10m above the ground. (b) The position of the 10 kg stone if it possesses a potential energy of 400 J. 4. A crane is capable of doing 1.5times 10^5 of work in 10 seconds. What is the power of the crane in watts?
Solution
4.3
(403 Votes)
Kaylee
Veteran · Tutor for 9 years
Answer
1. Work done is calculated by multiplying the force applied in the direction of motion by the distance the object moves. Work = Force x Distance. In this case, Work = 50 N x 2 m = **100 Joules**.2. Kinetic energy is calculated using the formula KE = (1/2)mv², where m is mass and v is velocity. **(a)** KE = (1/2) * 50 kg * (20 m/s)² = **10,000 Joules** **(b)** First, convert the mass to kilograms: 200 g = 0.2 kg. Then, KE = (1/2) * 0.2 kg * (300 m/s)² = **9,000 Joules** **(c)** KE = (1/2) * 1000 kg * (80 m/s)² = **3,200,000 Joules**3. Potential energy is calculated using the formula PE = mgh, where m is mass, g is the acceleration due to gravity (approximately 9.8 m/s²), and h is height. **(a)** PE = 10 kg * 9.8 m/s² * 10 m = **980 Joules** **(b)** To find the height, rearrange the formula: h = PE / (mg). h = 400 J / (10 kg * 9.8 m/s²) = **approximately 4.08 meters**4. Power is the rate at which work is done, calculated as Power = Work / Time. In this case, Power = (1.5 x 10⁵ J) / 10 s = **15,000 Watts** or **15 kW**.