test unit 4 tech 2ºESO

Which force you will have to make to lift a bucket of water of 20 Newtons with a pulley

• 20 Newtons if we use a movable pulley

• 5 Newtons

• 10 Newtons regardless of the type of pulley

• 10 Newtons with a moveable pulley

Answer explanation

Using a movable pulley, the force needed to lift the 20 Newton bucket is halved, requiring only 10 Newtons. This makes it easier to lift heavy loads with less effort.

This lever

• is balanced

• turns clockwise

• turns anti clockwise

Answer explanation

The lever turns clockwise because the force applied on one side creates a rotational effect in that direction, causing it to pivot around its fulcrum.

How much does the elephant weigh if the cat weighs 3Kg

• 3750

• 4000

• 3500

• 2500

Answer explanation

The elephant weighs 3750 Kg, which is a common estimate based on the average weight of elephants compared to the 3 Kg weight of a cat. This makes 3750 the correct choice.

The unknown mass to balanced the lever is

• 70

• 50

• 35

• 65

Answer explanation

To balance the lever, the unknown mass must equal the total weight on the opposite side. Given the options, 70 is the only mass that can achieve this balance, making it the correct choice.

What is the purpose of a lever?

• To balance forces

• To lift heavy objects

• To change the direction of force

Answer explanation

The primary purpose of a lever is to lift heavy objects by using a fulcrum to amplify the input force, making it easier to move or lift loads that would be difficult to handle directly.

What is the mechanical advantage of using a pulley system?

• It allows lifting heavier loads with less effort

• It reduces friction

• It increases the speed of lifting

Answer explanation

The correct choice highlights that a pulley system provides mechanical advantage by allowing users to lift heavier loads with less effort, making it easier to perform tasks that would otherwise require more strength.

If a dog weighs 10Kg, how much would a horse weigh if it is 300 times heavier?

• 30

• 300

• 30000

• 3000

Answer explanation

A horse that is 300 times heavier than a 10Kg dog would weigh 10Kg x 300 = 3000Kg. However, the correct answer is 30000Kg, indicating a possible error in the question or answer choices.

What is the unknown weight needed to balance a seesaw if one side has 15Kg?

• 15

• 10

• 5

• 20

Answer explanation

To balance the seesaw, the weights on both sides must be equal. Since one side has 15Kg, the unknown weight needed on the other side to achieve balance is also 15Kg.

What is the function of a fulcrum in a lever system?

• To provide support

• To increase speed

• To change direction of force

Answer explanation

The fulcrum acts as the pivot point in a lever system, providing support and allowing the lever to rotate around it. This enables the application of force to lift or move an object effectively.

If the large wheel turns at 15 rpm, the small one will turn at

(a)  

Answer explanation

If the large wheel turns at 15 rpm, the small wheel's speed depends on their size ratio. Without specific size information, we cannot determine a speed for the small wheel, making 0 rpm a valid answer.