Let the direction from left to right be the positive direction. What is the average force exerted by the wall on the ball if the ball is in contact with wall for 0.1 s? The ball hits the wall and bounces off with a velocity of 8 m/s to the right. |F| = |9.8 - 0| / Δt = 9.8 / (12 × 10 -3) ≈ 817 NewtonsĪ 1 Kg ball hits a wall with a velocity of 10 m/s to the left. Find the magnitude of average force exerted by the player if the impact time is 12 ms. |F| = |0 - 50000| / Δt = 50000 / 10 = 5000 NewtonsĪ football player kicks a 350-grams ball (at rest) and gives it an initial speed of 28 m/s. Initial velocity: vi = 25 m/s (assumed to be in the positive direction) So if you allow the time interval to be larger, you need a small force to change the momentum of an object.Ī 2000-kilogram car traveling with a velocity of 25 m/s is stopped in 10 seconds using a breaking force F. Stopping the same ball at a speed of 20 m/s but for different time intervals requires different forces which increases as the time interval decreases. (assume moving in the positive direction, vi = + 20 m/s)į Δt = 0.4(0 - 20) = - 8 Kg m/s, the minus sign indicates that F has the direction opposite the motion of the ball.

What force is needed to stop this ball inį Δt = m Δv = m (vf - vi), we need to stop the ball, hence vf = 0, vi = 20 m/s. You need to stop a 0.4 Kg ball that has a speed of 20 m/s. Δt is the interval of time over which the velocity changes from vi to vf.į Δt = m Δv = m (vf - vi) = m vf - m vi = pf - piį Δt represents the change in momentum and is called the impulse of the force F for the time interval Δt.Ī force F applied to an object for a time Δt gives rise to a change in momentum of the object.Īdvertisement Meaning of the Impulse Defined Above vf is the final velocity and vi is the initial velocity. What does the quantity F Īccording to Newton's second law, the net force F on any object is related to its acceleration a and its mass m as follows:Ī = Δv / Δt = (vf - vi) / Δt, acceleration is the change of velocity over time. Let us suppose that we apply a force F to an object for Δt seconds.

Impulse definition physics