class 8 chapter Force

While playing hockey in gym class, Timmy is trying to send a plastic puck across the floor and into the goal. Which of the following best describes the forces acting on the plastic puck as it travels across the floor and into to the goal?

• electromagnetic and gravity

• gravity and friction

•  mechanical force and friction

• Magnetism and friction

Which type of force could be used to pull up on a metal paper clip without touching it?

• force of friction

• force of gravity

• magnetic force

• elastic force

Which phrase best describes a gravitational force?

• a force that spins objects

• a force that pulls objects toward each other

• a force that can make objects both attract and repel each other

• a force that acts only when two objects are in contact with each other

Which of the following describes motion caused by a contact force?

• a sailboat moving on a lake

• a marble rolling down a sloped board

• a leaf falling to the ground from a tree

• a sailboat moving on a lake

On a cold morning, Jenny waited for the bus. Jenny's hands were cold, so she rubbed them together to warm them. Which force helped Jenny warm her hands?

• electricity

• friction

• gravity

• tension

On Earth, a brick has a mass of 10 kg and a weight of 5 lbs. What predictions could we make about the mass and weight of the brick on the Moon, where there is less gravity?

• The mass of the brick would be less than 10 kg on the Moon.

• The weight of the brick could be less than 5lbs on the Moon

• The mass of the brick would be greater than 10 kg on the Moon.

• The weight of the brick could be greater than 5lbs on the Moon.

During her last physical exam before takeoff, an astronaut was told that her weight was within the acceptable range required for astronauts. After she was in space for two weeks, her weight was recorded again. Which is the best explanation for the astronaut's significant weight loss?

• As mass increases, weight decreases

• There is less gravitational force affecting her in space.

• She lost body mass during the flight due to a decrease in metabolism.

• The amount of matter in a body decreases as the distance from Earth increases.

Your friend tells you the weight of a particular sample of chalk is 17.85 grams. Is there anything wrong with your friend’s statement?

• No, because grams are the right units for weight.

• No, because mass and weight are really the same thing.

• Yes, because your friend should have reported the mass in kilograms.

• Yes, because mass and weight are measured in different units.

Mass is the amount of matter an object is made of. Gravity is the universal force that acts between masses anywhere in the universe.

Which statement about gravitational force is true?

• The gravitational force between two objects depends on the shapes of the objects.

• The gravitational force between two objects depends on the masses of the objects.

• The gravitational force between two objects will decrease if the volume of either object is increased.

• The gravitational force between two objects will increase if the distance between the objects is increased.

An object is moved from earth to the moon that has different gravity. Why does the object's mass stay constant, while its weight changes?

• Mass does not change because it is a constant force.

• Mass does not change because it is resistant to acceleration.

• Mass does not change because it adapts to the change in gravity.

• Mass does not change because the amount of matter stays the same.