Speed, Velocity, Distance -Time Graph, Heat and Mode

Which of the following is a vector quantity

• time

• speed

• displacement

• distance

Answer explanation

Displacement is a vector quantity as it has both magnitude and direction, representing the shortest path from the initial to the final position. In contrast, time, speed, and distance are scalar quantities.

Which situation shows an object moving at constant velocity?

• The object is moving at constant speed in a curved path.

• The object is speeding up.

• The object is moving with the same speed and direction all througout its travel

• The speed of the object is changing every second.

Answer explanation

The correct choice describes an object moving with the same speed and direction, which defines constant velocity. In contrast, the other options involve changes in speed or direction.

Which of the following is a transfer of heat by radiation?

• The sun warming the earth

• A pot of water boiling on a stovetop

• A hot air balloon rising in the air

• Cooking food in a pan on a stovetop.

Answer explanation

The sun warming the earth is a transfer of heat by radiation, as it involves the emission of energy through electromagnetic waves. The other options involve conduction or convection, not radiation.

Which is TRUE about the particles when they lose heat?

• They move slower

• They stop moving

• They move faster

• They disappear

Answer explanation

When particles lose heat, they lose energy, causing them to move slower. This is a fundamental principle of thermodynamics, where decreased thermal energy results in reduced motion of particles.

Which of the following is the boiling point of water in Celsius?

• 0^oC

• 32^OC

• 100^OC

• 212^OC

Answer explanation

The boiling point of water in Celsius is 100°C. This is the temperature at which water transitions from liquid to gas under standard atmospheric pressure.

Which of the following is NOT a renewable energy source?

• 
• 
• 
• 

Answer explanation

Fossil fuels, such as coal, oil, and natural gas, are non-renewable energy sources formed over millions of years. In contrast, solar, wind, and geothermal energy are renewable, as they can be replenished naturally.

A microwave oven uses which method of heat transfer to cook food?

• Conduction

• Convection

• Radiation

• Adhesion

Answer explanation

A microwave oven cooks food using radiation. It emits microwave radiation that excites water molecules in the food, generating heat and cooking it quickly. This method differs from conduction and convection.

Which of the following is better conductor of heat?

• water

• oxygen

• metals

• plastics

Answer explanation

Metals are better conductors of heat compared to water, oxygen, and plastics due to their free electrons that facilitate heat transfer efficiently.

You run 10 meters to the right for 3 seconds and then walk 15 m backward for 2s.

Which of the following describes your speed and velocity?

• Speed is 5m/s, velocity is 1 m/s left

• Speed is 25 m/s, velocity is 5 m/s left

• Speed is 5 m/s, velocity is 1 m/s right

• Speed is 1 m/s, velocity is 5 m/s right

Answer explanation

You run 10 m in 3 s (speed = 10/3 = 3.33 m/s) and walk 15 m back in 2 s (speed = 15/2 = 7.5 m/s). Total distance = 10 m - 15 m = -5 m. Total time = 5 s. Average speed = 25/5 = 5 m/s, velocity = -1 m/s (left).

From the house, a boy walks 20 m east for 3.5 seconds going to his neighbor friend's house, and runs back home for 1.5 seconds. What is his speed and velocity?

• Speed is 8 m/s, velocity is 0 m/s east

• Speed is 8 m/s, velocity 0 m/s

• Speed is 40 m/s east, velocity is 8 m/s

• Speed is 40 m/s, velocity is 5 m/s east

Answer explanation

The boy walks 20 m east in 3.5 seconds, giving a speed of 20 m / 3.5 s = 5.71 m/s. He runs back for 1.5 seconds, covering the same distance, resulting in an average speed of 8 m/s. However, his displacement is zero, so velocity is 0 m/s.