8/9/2019 PHYSICS Workdone Ex

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CHAPTER: WORK, ENERGY & POWER

WORK1.

a. In Physics, explain what is considered to be work done. [1]b. Write down the equation to calculate work, and its SI unit. [2]

2. Identify which of the following cases is considered work. Explain you answer. [3]Case Description Work done?

Explanation

(a) A woman lifts a shopping bag vertically from

the floor and places it on her shoulder.

(b) A worker supports a bag ofgrain on his

shoulder and walks horizontally.

3. The figure shows a load that is to be lifted from the ground to a higher level along three different paths J, Kand L, with a crane.Which path requires the least amount of work?

Explain. [2]

4. Sam pushes a shopping trolley of mass 30 kg for 16 m.The work done by him is 2 kJ.a. What is the force exerted by Sam on the trolley? [2]b. Some additional groceries are added to the trolley.The trolley is then lifted vertically off the ground

for 25 m by a lift system that did 10 kJ of work.The lift moves at a constant speed.

i. What is the force exerted by the lift in raising the trolley? [2]ii. Calculate the mass of the added groceries. [3]

5. A tractor is pulling a fallen tree trunk along a rough road horizontally.The tree trunk weights2 500 N.The tractor is moving at a constant speed of1.2 m/s for 5 s.The pull force exerted by tractor on

trunk is 11 kN.a. Calculate the distance travelled by the trunk for 5s. [2]b. Calculate the work done against friction between tree trunk and the rough road.[3]

Higher level

ground

J K

load