CBSE Class 8 Physics Force MCQs Set 03

Answer: (b) Magnetic force

Explanation:
1. Magnetic, gravitational and electrostatic forces act without the bodies touching. Muscular, frictional and mechanical forces need contact.

Teacher's Note:
1. Divide forces into contact and non-contact types.
2. Non-contact forces act through space.

Answer: (a) gravitational force

Explanation:
1. Every object attracts every other object because of its mass; this is the gravitational force.

Teacher's Note:
1. Gravity is always attractive.
2. It is a non-contact force.

Answer: (d) newton

Explanation:
1. Force is measured in newton: 1 N = 1 kg m/s².

Teacher's Note:
1. Metre per second is the unit of speed.
2. Metre per second squared is the unit of acceleration.

Answer: (c) weight

Explanation:
1. A spring balance measures the pull of gravity on an object, that is its weight (a force). A beam balance compares masses.

Teacher's Note:
1. Weight is a force, mass is not.
2. The scale on a spring balance may be marked in newton or kilogram weight.

Answer: (b) bring it to rest, increase its speed or decrease its speed

Explanation:
1. A force can change the speed or direction of motion of a body, so all these effects are possible depending on the direction in which the force acts.

Teacher's Note:
1. The effect depends on the direction of the force.
2. A force along the motion increases speed, a force against it decreases speed.

Answer: (a) gravitational force

Explanation:
1. The force of attraction of the earth on all objects is the gravitational force.

Teacher's Note:
1. This force gives weight to objects.
2. It acts towards the centre of the earth.

Answer: (d) contact force

Explanation:
1. Your hand touches the balloon, so a contact force changes its shape.

Teacher's Note:
1. A force can change the shape of a body.
2. Pressing needs contact.

Answer: (c) muscular force

Explanation:
1. The force exerted by the muscles of the body is called muscular force.

Teacher's Note:
1. Lifting a bucket uses muscular force.
2. Animals also exert muscular force.

Answer: (b) push the ball, pull the ball or change its direction, all of these

Explanation:
1. A force from the stick can push, pull or change the direction of the ball, so all the statements are true.

Teacher's Note:
1. A force can start, stop or turn an object.
2. A hockey stick applies a contact force.

Answer: (a) the direction of motion, the speed or the shape of a body, any of these

Explanation:
1. A force can change the state of motion (speed or direction) or the shape of a body.

Teacher's Note:
1. These are the effects of force.
2. Remember: speed, direction, shape.

Answer: (d) frictional force

Explanation:
1. The rubbing of the tyre against the road produces friction, which gradually wears out the tyre.

Teacher's Note:
1. Friction acts between surfaces in contact.
2. It opposes relative motion.

Answer: (c) magnetic force

Explanation:
1. A magnet attracts iron nails without touching them.

Teacher's Note:
1. Magnetic force attracts iron, cobalt and nickel.
2. It is a non-contact force.

Answer: (b) muscular force

Explanation:
1. The pull given by your hand to stretch the band comes from your muscles, so it is a muscular force.

Teacher's Note:
1. A force can change the shape of an object.
2. The rubber band returns the force by its elasticity.

Answer: (a) empty space

Explanation:
1. A contact force needs the bodies to be in contact, directly or through an object. It cannot act through empty space.

Teacher's Note:
1. Gravity, magnetism and electric force act through empty space.
2. Contact forces need touch.

Answer: (d) friction

Explanation:
1. The force that opposes relative motion between surfaces in contact is friction.

Teacher's Note:
1. Lubricants and ball bearings reduce friction.
2. Friction acts opposite to the motion.