A large force acting on a body for a very short time is called:

An impulsive force is a large force that acts on a body for a very short time, such as the force of a bat hitting a ball, a hammer striking a nail, or a foot kicking a football. The impulse of a force is defined as the product of the force and the time for which it acts:

Impulse (J) = Force (F) × time (t)

By Newton's second law, force equals the rate of change of momentum. So impulse is also equal to the change in momentum of the body: J = F × t = mv – mu, where m is the mass, u is the initial velocity and v is the final velocity. This is called the impulse-momentum theorem.

Impulse is a vector quantity. Its SI unit is newton-second (N s), which is the same as kilogram metre per second (kg m/s), the unit of momentum.

The impulse-momentum relation explains many everyday observations. For a given change in momentum, if the time of impact is increased, the force is reduced, and if the time is reduced, the force increases:

A cricketer moves his hands backward while catching a fast ball, increasing the time taken to stop the ball and reducing the force on his hands.

A person jumping from a height bends his knees on landing, to increase the time of impact and reduce the force on the legs.

Glassware and electronic goods are packed in straw, thermocol or bubble wrap to increase the time of impact during a fall.

Cars have crumple zones and airbags, and high jumpers land on soft foam mattresses, for the same reason.

A karate expert breaks a brick by hitting it quickly, applying a large force in a short time.

Vehicles have shock absorbers to reduce the impact of jerks.

Why not the other options?

• ✗Torque is the turning effect of a force about an axis.
• ✗Pressure is force per unit area.
• ✗Power is the rate of doing work.