Question

(non calculus based physics)

Question 1

An Olympic weight lifter lifts an 1800 N set of weights from the ground to a vertical distance of 2.20 m above his head. Assuming he moves the weights at constant speed, how much work does the weight lifter do?

Question 2

A 4.5 kg trunk, initially at rest, takes 2.0 s to slide 2.8 m down a rough 25° slope. Calculate:

1. the work performed by the force of gravity.

2. the amount of mechanical energy lost due to friction.

3. the amount of work done by the normal force between the trunk and the slope.

Question 3

During a baseball game, a 75 kg ball player begins sliding into third base while moving at a speed of 4.2 m/s. There is a coefficient of friction of 0.73 between his clothes and the ground. His expertise allows him to slide in such a way that his speed is zero just as he touches the base. Determine:

1. the amount of mechanical energy that is lost due to friction acting on the runner.
2. the distance the runner slides.

Question 4

A secret agent fires a rifle with a tiny 2.2 g bullet, which leaves the barrel of the gun at a speed of 335 m/s.

1. Find the kinetic energy of the bullet.

2. What is the average force that the expanding gases exert on the bullet as it moves down the length of the 60-cm barrel?

Question 5

A 2200 kg vehicle is affected by the actions of two forces as it travels down a level road: a 1200 N force exerted by the road on the drive wheels, and a 925 N frictional force. Assuming the vehicle starts from rest, calculate its speed after it has traveled a distance of 30 m. (Hint: use the work-energy theorem.)

Question 6

A 1.20 × 103 kg mining car sits at the top of a hill, at point A, before moving 65 m at an angle of 42° below the horizontal until it reaches a lower point, B.

1. Use point B as the zero level for gravitational potential energy. Calculate the potential energy of the car at points A and B, and determine the difference in potential energy between these points.
2. Repeat part (a), using point A as the zero reference level.

What is the work done by the force on the packing crate as the crane moves these distances?

1. from x = 0 to x = 6.0 m

2. from x = 6.0 m to x = 10.0 m

3. from x = 10.0 m to x = 16.0 m

4. Determine the total work done by the force over the distance x = 0 to x = 16.0 m.

Question 13

Consider a simple pendulum that is 3.0 meters long. It is released from rest when the support string is at an angle of 20° from the vertical. What is the speed of the mass at the bottom of the swing if we ignore air resis- tance or any frictional forces?

Question 14

Batman and Robin, who have a combined mass of 165 kg, begin a swing on a 6.0-meter-long super-strength composite cable at an angle of 35° with the horizontal. At the bottom of the swing, Robin, with a mass of 75 kg, is released. What is the maximum height of a windowsill that Batman can land on after completing his swing?

Answer 1

Solution: 1

Work done by weightlifter = mgh

=(mg) x h

= 1800 N x 2.2 m

= 3960 N-m

= 3960 Joule